Pro athletes watt variaton during season (taper, peak performance)?

Trying to redo post for easier question

How does the training watt values of the proffesionals variate during a year?.
If they were to follow the trainerroad hard volume plans for the intervall workouts.

The reason i wonder is that it seems the pros good/bad days is so common and the difference is so big. And what is the reason theire perfomance variate so much?. Do they train themself so far into the basement that they just don’t have the power until recovered again?.

For myself i feel that my performance is almost always how i would expect ± a few % watt.
And for year round my FTP training watt won’t change by much if there is no big sickness or anything like that.