this paper is discussing mechanisms limited to the J&J and Astrazeneca vaccines
(This is not my specialty at all, just summarizing the abstract & what other commenters wrote since nobody replied to you yet)
I'm sorry about your father-in-law.
I don't know, that not my area either. My main two points are that if covid itself can increase risk of stroke and now some covid vaccines can too, then I wonder if other covid vaccines might have contributed to this anecdotal one. The second point plays into the first. I would be less likely to question it if we had better reporting in the VAERS system.
He actually seems fine now, so he recovered quickly.