Gleason 8 is, by definition, poorly diferentiated, I believe. It's not whether differentiation has changed that determines whether the delay it's what those cells did, where they went.
Yes, I think you are overthinking. But that's easy for me to say to another. I do it all the time.
Dx Age 64 Nov 2014, 4.3
BX 3 of 12 cores positive original pathologyG6, G6, G8 (3+5)
downgraded to 3+3=6 by Dr Epstein, JH
RALP with Dr Ash Tewari Jan 6, 2015
Post surgical pathology – G7 (3+4), ECE, Margivns, LN, SV all negative
PSA @ 6 weeks 2/15, .<02, remained <0.2 until January 2017, .02
My Story: tinyurl.com/oo9x4aq