I found that with Tmax films, a good prewash (prior developing) at 21°C for 5-10min removed most of the film sensitizing dye. Remainder of dye was then easily removed with extended fixing (requirement for Kodak stocks) and final wash.
Yes, a prewash removes part of the anti-halation layer but also a few other things in the emulsion, which are added to aid development. In my opinion, it's better to add some wet time post development. A second fix, a treatment in HCA, and a brief wash in between are particularly useful to remove the dye completely (not that it does any harm).