It always appears that the folks least caring about tags and most cavalier about them aren’t the ones in the financial area where it makes a lot of difference.
Generally, If you’re not buying 100k plus cars, you can afford to not care about authentic tags and documentation. People buying upper end cars deserve to not be defrauded by fake tags whether you care or not.
Part of dealing with 100k plus cars is doing your due diligence about the origins, documentation, etc.
If you're dropping big money on a hemi car or something I would hope you're checking to make sure the build sheet, VIN, fender tags, body numbers, engine and transmission numbers, etc. corroborate what you're purchasing.
What about my car? It sat outside long enough with the windows out/down that there's no chance of a surviving build sheet. It's a '68. The dash was sold and subsequently reunited with the car so it has it's VIN. The fender tag was also separated from the vehicle but retained by the owner. I am now in possession of all 3. The tag decodes to match what's there. The original paint on it matches the car. There's no build sheet to connect the order number on the data tag to the VIN which via the dash frame has been separated from the body.
If I end up restoring the car, the fender tag has a hole rusted in it. It's small, and between numbers. It definitely doesn't interfere with reading or decoding the tag. I would try to procure a replacement so it looks nice. Is there something immoral about that? Especially if the original tag is retained as part of the car's documentation?
A '68 wouldn't have had a VIN on the engine or trans, so procuring date coded replacements would really make the car as good as it could ever be. Would I represent it as original, numbers matching? No. Would its value be perceptibly less than a documented, numbers matching example?
I think it's up to whomever is laying down the cash.