General comment here...
PTC has many examples over time where many document sub types exist in a test Windchill system and all are available to users to select in all contexts for "New Document." But - I've seen pretty much every admin at least attempt to limit what sub type(s) are created in each context, removing the choice from the user.
In suggesting lots of times to PTC to allow this to be configured more easily vs. using Deny or some very non-elegant approach, the suggestion is always met with very little interest.
It seems that PTC should address this thru a simple GUI - it's a universal need for pretty much all systems.
We have most Products set up to accept most Document subtypes but then have about 25 special-purpose LIbraries, each of which only is allowed to contain one or two Document subtypes. In these Libraries the New Document wizard immediately moves past the type selection if there is only one type allowed, removing the choice from the user.