I just discovered a method to label prints: When I printed a case in Sunlu PETG-CF, I overlooked that there was a small rest of Sunlu Silver Silk PLA on the plate from a previous print. I fused nicely (or horribly, if you consider the lost print) with the print. Step 1: Print text mirror-inverted with 0.2mm nozzle and Silver Silk PLA. Step 2: Print object with 0.4mm nozzle and black PETG over it. The plate was sprayed with 3DLAC before the PETG print, in case that matters.
Beside of the nozzle swap, I don’t see any benefit (for AMS users) instead of doing a regular labeling in Bambu studio. Did I miss something of your post?
Additional hint: Your method will only work if the pre-printed part is not recognized by any sensor, incl. the auto-bed-leveling.