I think you are 100% correct and as we know sometimes the wheelchair boarding can take a while especially if they have to transfer someone to the on-board wheelchair and take them well into the back of the plane, get them off of that and into their seat.

I also had the fun experience recently where they started boarding for some unknown reason before the Captain was on-board and then the plane took a mechanical for 3 hrs.

I've also had more than one occasion where there was no notification and I stayed in the lounge a little longer only to get to the concourse where they are now paging me for 'final call' and expecting me to run.

It's better I think now that they have the progress meter in the App, but I still don't trust the notifications 100%.