At that point it's not a debug connector anymore. Note there's a pseudo-standard for V.24/RS232 on RJ45 already, and nobody uses it for debug connectors since (a) you'd need a RS232 transceiver and (b) RJ45 connectors are honking huge.

The point is to shave off the last cent, which is why you get a possibly-unpopulated 1×4 or 1×3 2.54mm header. Bonus points if the manufacturer designed series resistors into the board (let's say 0402 or even 0201) and left those out too to save the last 0.01 cent.