It’s also important to be aware of how much hard sprints can throw NP into wildly irrelevant values thanks more to the non-linear math than physiological relevance.
For example, I did Bays +1 yesterday using the screwed up outside workout version. Mostly high Z2 endurance but with 6 20-sec sprints instead of the targeted 4. Did the sprints at ~3.1 X FTP instead of target ~1.8 X.
Two extra sprints and going harder on them skews the TSS from a target of 84 to an actual of 167 in 95 minutes. Was also the highest NP I’ve ever seen for 95 mins. But there’s no way I could actually do those watts for 95 mins steady - doubtful I could even do it for 60 mins.
At the same time, I’m also not nearly as fatigued as I might have been with a 95 min all out TT or other more steady efforts to try to achieve that same NP / TSS.
Point being, be careful on NP conclusions if you have a few big sprint efforts on a group ride or workout - the math goes pretty crazy when you start taking things to the 4th power 
(ps - for those that use Rouvy and chase the career seasonal TSS metric - this is a very useful hack to rack some extra TSS up quickly 
)