Question - Isn't the only T-FHSS SR compatible model currently available the R334SBS (which has an external antenna)? If this is the case, while yes it would be true that Futaba has antenna-less offering(s), the response time gap would be an even wider deficit than an M12S-482 combo.

We are back to personal preference. Having gotten away from antennas with the 482, I personally don't ever want to go back to them. No antenna AND faster/est response time is a win-win.