So, under the WIPO Copyright Treaty burning a DVD-A ISO from a commercial disc isn't legal, even if you own that disc. In the UK it would be the 2003 copyright regs: https://www.legislation.gov.uk/uksi/2003/2498/regulation/24/madeI include burned DVD-A in my definition of "Universal player". This is an entirely legal disc format.
I appreciate the insistence that it should be allowed, and I understand that you can technically author a DVD-A disc yourself, which I recall you've mentioned doing in the past But given that the vast majority of such discs are technically infringing, this doesn't strike me as being a winning argument. And frankly, you're just going to exasperate yourself demanding it.