I doubt any of those reddit posters have done due diligence. LG DOES NOT cover burn in warranties anywhere, as it is indeed an inherent property of the OLEDs. I didn't click a photo, but I was looking for a TV for my parents this Diwali, and the 4/5 years comprehensive warranty on LG OLEDs was tempting. I checked the exact offer brochure in Croma and it very clearly said burn in is not covered.
Having said that, we know through reddit that LG has offered 1 time replacements mostly in western countries without much trouble - though YMMV. I don't know of any such case in India (I have a C8, and the warranties were crazy expensive 2 years back - 50k-ish for 2 years, around 90k-ish for 3 years - almost the cost of the TV).
UK has a mandatory 2 year minimum warranty by law. I believe anything extra is on the onus of the seller - they probably have more margin than what Indian sellers have (though considering LG OLEDs are manufactured in Pune, India, the import laws should not apply). If you purchase the extra warranty from these sellers - VS, Croma, RD etc, generally it is significantly cheaper than official warranty (even 2 years back, they were 1/3rd the cost of official warranty).
Considering the official warranty price during Diwali, it is a no brainer to get it officially. I checked at so many places but couldn't get a warranty for my C8 at a price anywhere close to those.