My guess is that, as long as the plane was catered and they had something they theoretically could serve you, it is very much a YMMV situation depending on your FA. Especially with the RJs where a more junior FA doesn’t have much experience with the vouchers.

As mentioned upthread, the agent may not have or be able to use the scanner to redeem the voucher, or they may not even know how, but truthfully that same issue happens often enough to me anyway on mainline flights over 500 miles when I try to cash them in.

Usually if the FA can’t figure the scanner out on how to redeem the voucher, they just give me the drink, and move on.