Honestly, I don't generally let factors from other paths influence how I view the one I'm on. In my opinion, they should be seen as "alternate universes", so really the fact that Maya doesn't pursue you if you don't date them doesn't necessarily have much bearing in the case where you do. Again, remember that Josy had a much longer time with you alone for those type of feelings to build, so Maya is essentially starting from behind in terms of developing an emotional bond even on the throuple path.
Then again, I'm sure my perspective is coming from a very different place in life since I'm about two decades older from the sound of it.
Honestly, while this might be good advice for some guys, there's plenty of others that don't really feel the need to sow the wild oats and would be happier looking for emotional relationships earlier on. In the case of Maya and Josy, by the time you commit to a relationship with them you've already been "together" for 2-3 months, which really isn't that long of a time to date before discussing becoming exclusive. After all, you're not marrying them, just deciding that the bond you feel with them is important enough that it's worth dedicating your full attention to in order to see if it might be a worthwhile future.