Really don't have any helpful answer.
Fwiw, our family procrastination on a will was different, siblings who chose to endlessly put their energy into fighting with each other, rather than getting on with it.
They took 3 yrs to get a grant of probate. This caused two issues-IHT, and upset beneficiaries.But, apart from the IHT, there didn't seem to be any reaction from HMRC, or anyone else official.
That's not to say there can't be any other problem, but not an obvious one.
It's such a tricky matter, to help a stubborn elderly man ,in such a way that they don't have to admit that they need help. It seems to be necessary to not imply criticism. Eg, if I asked my Dad if he wanted some help cleaning, he'd have said no, so I used to visit with my dog, and then say,"oh, no, she's left hairs everywhere,no, I insist, I'll just run round with hoover".
Sorry, off topic, but an example of going round the houses so he didn't lose face.
Would it be worth inventing, eg a neighbour who's found the forms and paperwork difficult, to bring the topic up in a neutral way, giving him a chance to say/or you to ask/ how he's finding it?