Yerp - that's perfectly true, Samche - but no doubt there are also some hoops in other regions for which jumping is required, while for you, it is not.
Think about it - if the matter of EHIC is standardised across BG, what are the alternatives? Either to NOT ask for it - or to make LTR applicants take out rather expensive, meaningless and pretty worthless private health insurance policies. Seriously, which do you think BG immigration offices are more likely to go for?
Incidentally, I'm not even sure if you would be able to get a cheap 5-year or 10-year private medical insurance policy just to fulfill the requirement - so you would then have to go to BUPA or similar, which are rather less than cheap, especially for older people. Or you get a one-year travel policy and would then have to renew your LTR every year.
Like you, I wouldn't dream of trying to submit my EHIC to pay for BG treatment as I am no longer a UK resident in that respect, but live in another (non-EU) country currently, and not in BG.