No, you actually want to reverse-engineer the PCB so that you have schematics. That allows you to more easily replace components with cheaper alternatives and/or modify the firmware to continue working on your unintended hardware. (Fake products typically replace the on-board components with cheaper variants, like using lower-rated caps, to squeeze out a tiny bit more profit margin. Like really in the $1 per 10k units range.) Plus PCB x-ray is a common thing that also reputable manufacturers do for quality control or security assurance (e.g. Is there a HW backdoor in this mainboard?) so you can just book that as an affordable service. I remember Siemens recently bought a PCB RE provider, but I can't find the news article anymore.

To give you some price ideas:

10x10cm 4-layer PCB x-ray and RE: $200

STM32 firmware dumping: $700

EEPROM dumping: $300

The STM32 is the most expensive because you need to decap them to get the hardware encryption key. But it's still A LOT cheaper than building your own firmware from scratch.