Unit Transfer - Commander Signature Required?

Current E5, 7 years TIS.

I'm currently in the process of transferring to an instructor unit. The incoming unit has assured me that my current commander does not need to sign off on it, only the incoming commander does. I've already filled out the 4651 but I guess it can't be submitted to ippsa without my current commanders signature.

My current commander is potentially holding me in place until the fall so that I am essentially forced to attend AT instead of transferring prior to AT and earning my instructor certification. Kind of holding me an extra few months.

Is this true? I'm looking through regulations and I'm unsure. If so, definitely seems shitty.