Benefits I am/was Eligible but did not known

Hello, 

I have question in regards to benefits eligible for in past. For example: 

Mr X had a accident in December 2019 which affected his ability to work from 2019 Dec to March 2020.(Accident was in workplace and caused due to Health and Safety breach by employer.)
He does not claimed any benefits in this time, he had a partner who support him financially during this period of sickness, he got only 1 week sick pay and then never been back to workplace. When feelt bit better he found and start new job end of March 2020.
Then in 2022 sustained multiple bones foot and ankle fracture and at the point he is full time employed since 2020 March no breaks he and his partner receiving UC since  May 2021. 
After a 4 weeks and lower income received UC question him to look for more work, then he is telling them actually and that he is on sick note since June started ( couple is not aware of need to report Sick notes) as advised they put on UC sick notes and he is referred for WCA. Their UC is paid on time with only income from his SSP and partner part time wages. 
He have his work capabilities assessment In October and later in the same month he have outcome decision call to accept claimants commitments from UC which he did and he is told he will received  backdated payment from the day he report his sick note, and the changes will be showing on next statement. 

Then days later he have another call from UC and he is again asked about his health con. then someone from UC ending call saying its all fine.

Next days he have letter available on Journal saying he was assessed and he have LCW. Couple does not really get in to that matter as they are still thinking that they have to wait for next month payment to see help eg. backdated payments and current change of additional benefit on UC statement they do not know exactly how much but lower income affecting their finances and they struggle a bit. 

On the start of new month they question when and how much will be backdated on UC statement as they need to know if they would be able to cover all rent etc as they been short since sickness started. The replay they get is that they will not get any backdated payment and they UC will not change as he was only awarded LCW not LCWRA. 
Couple is confused and requesting MR and assessment report sent to UC from HCP. 

They HCP assessment says 14 months prognosis need reassessment after 12 months 
Report also says exceptional circumstances Yes, due to high risk factors which would affect claimant or others if he would not be found to have limited capability for work  this is recorded under Special and Exceptional circumstances. 

When they question this to UC saying that he was awarded LCWRA under exaptational circumstances UC replay that they are not entitled to additional amout as health condition was not reported before 2017, when they did not ask about any additional components, only why this is not LCWRA if HCP report showing expectation which mean he was not LCW but LCWRA. 

Mandatory reconciliation also refused change from LCW to LCWRA. 

Couple quite and decided to apply for ESA on HMRC website to get help after his sick pay ended in October 2022. 
After that in December they received letter from DWP he is eligible for ESA C and ESA IR but until now he need to reported sick notes and submit them online on HMRC website.  Couple Called DWP and found out that they are not aware at all that he had WCA and advised that they will asked UC to provide that as well as they should do on Jurnal request to send WCA outcome to DWP ESA. 

Shortly after they received call from JCP from local JCP lady they seen before and she literally shouting at couple said they have to not to claim that benefit as this would not change anything and they will not get any money as not that's it. 

This raised even more concern, as this was not normal call and amout of anger and way the conversation was sound like someone really does not want to let them get that ESA. 

Any thoughts on the story as this is based on life example I would like to find out if other people would see what I see and how you understand that. There will be more information to follow but please make some comments as this would be useful to see how someone with hopefully wider knowledge on benefits system and how this works give idea what happened and what documents people could request to find out if they are paid correct amout of benefit and they are not missing out by lack of help and advisory from UC, even more they sound like they want you to be worse off.

Is UC hiding some information? Legally are they liable to inform claimant of current eligible for the household support or eligibility to other benefits when off work sick...

What I see I will comment if someone would be able to add any information and how this issues could be addressed to UC and where Would be helpful...

Thank you. 

N.