Invoice vs Tax Invoice on .pdf

The .pdf version of the POS receipt recently changed from the header saying “Invoice” to “Tax Invoice”. As we use this form for our DTC consumers, and reflects our brand, not happy with the change. When I asked support to have this changed back I was told this has always been the format, and everyone has to use the same template. Obviously it has not always been like this as I have copies of invoices clearly showing the difference. I posted this to support and they suggested I reach out to all of you to see if anyone else has similar requests or issues with the .pdf version with the header of "Tax Invoice"
I have do a few questions:
Why do we all have to use the same template? Seems archaic to me, but I will be the first to admit this is not my area of expertise.
I saw in a lower post that someone had asked about a “Tax Invoice” so was it changed without reaching out to their customers to see if we all wanted this change?
Perhaps someone can explain why we would want our invoices to say “Tax Invoice”.