Unlimited used to mean unlimited.

In a marketing context it never meant that, same as "satisfaction guaranteed" doesn't mean what you expect. It really means "product has a fixed price with vendor defined service level" vs "defined service level and variable price according to usage". "Unmetered" might be a reasonable shorthand.

Oh, it's totally metered.

Now it means “caveat emptor.”

That's true and practically every statement made in an ad aimed at the general public should be taken with just as many buckets full of salt grains.

If an ad for a lab oscilloscope were made that way, nobody would ever buy it.

This isn't as bad as the recent campaign by Rogers in Canada for their "infinite" package.

https://mobilesyrup.com/2019/06/13/rogers-unlimited-infinite...

Taking a page from Freedom Mobile, the new plans offer ‘unlimited’ data in that they don’t include data overage fees. Instead, once subscribers go over their monthly data allotment, Rogers caps their data speeds at 256Kbps until the start of their next billing cycle.

10GB full speed.