ok, let's examine, Guffaw said that for the non-genetically gifted doing 20-min HIIT workouts is plenty and doing more leads to overtraining. putting semantics of overtraining aside, 1) it's not enough, 2) in itself, it does not lead to overtraining, 3) it certainly has nothing to do with not being genetically gifted, and 4) has nothing to do with injury, illness, or stalled gains. it's normal. being tired after workouts and needing recovery periods is completely expected to increase performance. even overreaching is fine. you certainly would welcome a player on your team that went above and beyond his normal workloads during games. he might need an extra rest day. no big deal. same with stalling. stalling is normal. it may be a consequence of insufficient calories, technique, programming, increased strength levels, or a combination of all those things. nothing to do with actual overtraining.
now for overreaching/overtraining. read it a bit more carefully. there are biological factors that dictate whether you can fully recover after your workout. the time periods are important because recovering fully from overreaching (a matter of days) is hundreds of times easier than recovering fully from overtraining (a matter of months). it is also important to note how those are different from actual injury and illness.
and finally, if being told you are wrong is considered rude, get a thicker skin. this being a hockey board, and the internet, i'd think you'd be used to much worse.