While interchanging the terms Sweet Spot, Tempo, and 90%FTP is pretty much semantics, what one does with that intensity (ie. the duration and # of repetitions of that duration during a workout) are not. To train appropriately for a specific discipline, what one does with that intensity level would likely be different things. Coaches will vary in that methodology, as will riders without coaches training for events. Riders with relatively little experience will often adhere to a specific methodology. Riders with deeper experience will often do what works based on their training history and the results derived. The only way to know for sure is to maintain training notes and reflect on the results over time, the more time the better the results.
When Boardman busted the hour record, I doubt he would have won The Tour of Flanders with the same training approach. When Tom Boonen won Tour of Flanders, I doubt he would have achieved the hour record using the same plan. They both likely spent good amounts of time at 90%FTP but how much and how often is anybodies guess. That however is based on nothing but my personal feeling and what information I've soaked up during my time on the bike.
Which btw is not to say that FTP will not increase during ME specific workouts, and ME will not increase during FTP specific workouts.
My notes from Friel arrive from his 4th Edition Bible (2009), and my notes from Hunter Allen arrive from his recent Battenkill training plan and his contributions to ROAD Magazine. What I do know with regards to building ME Allen is quoted as writing "There is no easy answer".
