Soooo…feelin’ pretty dumb right now. 
Was doing a VO2 workout tonight and got to thinking…then it dawned on me the answer to my question:
My lungs are better trained than my legs. 
Plain and simple.
Thinking back to the training I did last season, it was only 5 hours/week with 2-3 hours of that doing VO2 sessions (the rest were attempted over-under workouts). Then I spent the summer doing Z2/3 and/or Z5/6…with zero threshold time.
It’s no wonder I’m crying doing 90 min O/U sessions.
I’ll just shut up now and keep riding my bike.
Let the weeping continue… 