It could be many factors that play here, some just are overresponders or vice versa.
Shbg plays a big role too. Hell, even half life of drugs can differ significantly from person to person, that's why some studies put out numbers with ± symbol. I know I metabolize drugs faster than normal, so for me injection frequency must be on on point, I use TU for a cruise and it's almost perfect.
It is possible that weight or lbm affects TT. But again everyone is so different it's hard to guess, since I don't change too much anymore I can't really compare it now. It would be interesting to see how (if) it changed over time.
Yeah, that's quite low. But again we don't know who that person is, maybe he accidently skipped one injection without noticing, maybe he accidently injected subq and his response is different, or mayve he needs to adjust his inj freq like yours or eod due to shbg/fast metabolizm.
For all we know, it could be anything in between or not related at all. That's why it's important to adjust and find what works for you.