Every team needs to bring in high quality players of the same birth year to supplement their priority draft picks if they want to contend. When was the last time a team won the OHL with only their own draft picks on the roster?
These players are added in different ways. Free agent signings, Import Draft selections, flyer picks that they get to report, or trading for players at various stages of their OHL careers.
Most teams add these players through trade at 18/19 years old, because teams understandably don't want to let go of good players at the beginning of their OHL career. However, some teams not named London do add players at 16 (eg Porter Martone).
Again, London did trade away a great player at the end of his OHL career at the trade deadline (Robert Thomas) in a year they weren't contending as other posters have pointed out, so why is it being suggested that this approach is wrong when other teams do this too?
London has also pissed away picks at the deadline for 19 year olds and not had success (2017 - Mitchell Stephens and Mitchell Van Sompel).
Other teams have also tried to bring in 16 year olds that wouldn't report elsewhere a la London with Dickinson and Brzustewicz. Windsor almost got past Hamilton in 2022 with Cuylle after he wouldn't report to Peterborough. Other teams have traded for the rights to good players but found that it is sometimes harder to get them to report than they thought (and London is not exempt from this either - William Moore comes to mind).