Number of tier point doesn't matter much for these situations, however not all GGL's are the same in BA eye. It can go down how you book your flight, as if you are using your corporate travel agent versus self booking. The moment you use corporate travel agents then BA knows who you work for and that can put you in a different category. It does matter what fare class you book your flights even if you use corp travel agents. Also large and important companies can nominate important travellers (who doesn't have to be key decision maker) it is possible that one of your colleague made onto that list whilst the other one is not.
The onboard upgrade to F sounds unrealistic to me ( I mean it can happen once but def not constantly) as if he is super important to BA, BA would do that during checkin prior boarding. Same goes with the better recognition onboard as it's a total hit and miss mainly because cabin crew not easily able to see any difference between GGL's. Sometimes they can't see the tiny difference between gold and ggl.
The escort is not a GGL perk, not official at least. It happens sometimes but at the moment I believe the team is soo small that they can barely able to great all Premiers. If they would have to do that for all GGLs then the whole First checkin would need to just do that. Same with car pickups. It can happen but since covid it scaled down to much smaller scale.
So I think above is more of a nice story and perhaps your junior colleague just wanted to wind up the manager.

On the positive note the BA events are coming back soon. (no idea how soon or when) so let see who makes it to that list.