Of course they do. But see here http://www.milevalue.com/dont-pay-the-75-close-in-fee-on-united-trick/ MMS posted it after he did. So no Taynes on MMS.
Is there a better way
No need to spell it out.
That's what DDS is for.
Is there a way to book a mixed class RT (Y one way, J the way back) and not pay J fare for the whole trip?
Just book a regular trip. That is the default.
Shhhh
Why is it different then pggm?
For the same reason it's different than churning.
Churning is officially allowed. Pggm is a glitch in the system