to be clear, unless something has changed recently, the no residuals is enshrined in the fare rules on every fare since ‘no change fees’ started. Even on tickets issued directly through UA. The ability to get a residual on tickets issued directly by UA is a result of a policy that was implemented some time after that (there was a period where even UA booked tickets didn’t get it). So any ticket, by default, doesn’t get it.

TAs need to abide strictly by the fare rules, so you are correct that unless UA has decided they can give back residual, they can’t.