Hi
Just my pennies worth. FTP is just a indicator of what your current fitness level is. 2–5% difference well … It affects a little the zone you are working in but if you are doing 88-94% SS training then you are pretty close even with a bit of tweaking.
Abbey is one of the easiest sweet spot workouts, i use this in the Recovery week for a couple of the easy recovery rides, i find i do not get so bored in the recovery week this way.
Even if you are 20 watts out with FTP estimation, you can add 5% to the workout by just moving up the workout %, if you feel okay with that, try doing something like Mary Austin and if that is achievable then, reset your FTP to that value. Caution, watch out that you do finish all the workouts. And watch out for burning out. Maybe okay in the 1st week but by week 5 you may struggle.