You’d be surprised what modern neodymium drivers in a well designed enclosure can accomplish bass-wise. Though you are right in that the laws of physics have not changed, and something has to give, usually what has “given” is the increase in power output of small amplifier boards, thus allowing DIYers (like myself) and manufacturers alike to throw more power into lower efficiency, but higher mass (and thus more bass in a smaller enclosure) drivers.

With Hoffman’s iron law where you can have two of efficient, low, or small, it seems like efficiency is what has gone down to get more bass extension while keeping enclosures small-ish.

I’d be happy to provide photos+construction details of one of the portable speakers I made, and frequency response measurements if you’d like, to illustrate this.