This would require lab tests to be performed on out of date Huel which is not something the average user can do.
The nutritional profile will not fall off a cliff. Even 6 months past it’s date, if stored correctly I would expect the vast majority of it’s nutritional profile to be intact.
Ultimately though you are seeking information which nobody can provide you with. Huel have a date on their packet which they stand by and anything beyond that is your decision. As a company they can’t be advising people to consume products past their date as they could end up in all kinds of trouble. We know though that BBE dates are set FAR too conservatively but legally companies have no choice.
I have eaten a current version Huel bar 6 months past it’s BBE date as an experiment and to be honest it tasted the same as one in date. I push food far past its BBE as I don’t like wasting food. I have cows milk at least a week past its date and it’s still fine.