Normally I would agree with you on Mercedes and I do still somewhat feel that way. Mercedes has been visibly struggling with the porpoising effect though since the first test and they haven’t seemed to work that out yet. That has to make it very difficult to get your breaking zone perfect with the car bouncing like it is.
That being said though, these announcers certainly love to play up these FP sessions. So many times last year, “such and such driver is way off the pace, it’s going to be a bad qualifying session for them.” To then have Such and Such driver get the pole.
With Mercedes, it seems they know they’ve got the pace, so I think they work on other race pace stuff during the practice sessions.