What made me think Ledger Nano replicas exist is when i saw them on eBay for 20 usd each and they had lots of sales. It was also New in Box. I just checked and they are no longer selling them that cheap, it was few months ago when I saw them. Or they could have bought original ones and did the custom scratch card with their own personal seed like this and sold them cheap to attract buyers:
I don't think it pays for anyone to modify hardware wallets and then sell them somewhere as originals, because apart from such modifications requiring expertise - you can never know in whose hands such a device will fall, maybe to someone who will save a BTC worth $100 on it. What I think poses a greater danger is a targeted attempt to deliver such a modified device to a person who is already known to possess a significant amount of crypto - and the ideal targets for this are those who keep their crypto online.
Of course, I'm not referring to pregenerated seed here, but to modifying the hardware that could potentially allow an attacker to take possession of the seed - yet this is still an unexplored area where hackers are certainly working.