Don't take our word for it, read
one of the XYOSTED studies. "Relative to 200 mg IM TE, the two doses of 100 mg SC TE (week 5 and week 6 combined) demonstrated similar AUC(0-inf), suggesting that
the bioavailability of TE is similar whether administered SC or IM."
The general statement should be that IM results in
faster absorption than SC for most, not better absorption. This is reflected in the shorter apparent half-life with IM.
The unexpected result is your reduction in trough TT with the move to SC. Typically as drug half-lives increase the serum hormone trough levels increase while peak levels decrease.