Disabled Bus Pass

All local authorities do differ slightly. Mine for example does not offer companion bus passes at all. No exceptions.

All have automatic and most have discretionary criteria.

As you've found out, you don't get the correct PIP points for a particular descriptor to qualify automatically. They look specifically at mobility as in mobilising, not journey planning or other difficulties to qualify automatically with PIP.

You can still apply under discretionary criteria

"Disability or injury which has a substantial and long term adverse effect on the ability to walk – Eligibility code D"

using medical evidence. You might be asked to do a medical assessment.

https://www.hertfordshire.gov.uk/services/adult-social-services/transport-for-older-people-and-disabled-people/bus-passes-for-disabled-people.aspx#DynamicJumpMenuManager_1_Anchor_1

You can still apply for a bus pass as advised with other medical evidence.

I did my applications (outcome 1 x2 year bus pass, then upon renewal was given 3 years) with a paid for GP letter. I wasn't asked to do any further medical assessment. I now do qualify automatically.

It's because your local authority only accepts PIP awards with 8+ points for Moving Around to qualify automatically for a Bus Pass.

Motability is a separate organisation with no criteria beyond an Enhanced PIP award with a minimum length, and a Blue Badge has different, wider criteria under your local authority compared to a Bus Pass. They are all different things with different criteria.