Thats actually a huge factor that I, and many people forget about when comparing paths. TOI at this age can be huge for development. Joining a CHL team, especially the Knights, you're a 16 yr old kid joining a team with kids 1-2-3-4 years older than you that are trying to win games and a Memorial Cup. You're competing with older kids for that ice time, and those older kids will give the team a better chance to win, so they often get the TOI.
Joining the NTDP, youre entire team is the same age, and TOI is much more evenly split through all lines. The NTDP isnt focused on winning the USHL, it's purely for development. Sure in his Draft season or D+1 Stranges will be getting much more time, but the NTDP clearly offers better chance to develop and time to grow in your pre draft years, where it can make a tangible difference i would guess. Obviously there are CHL advantages, but this is just one example.
simplified CHL to an extant is winning > development, NTDP is about development > winning