The devil is in the details. In older designs there was circuitry between the output transistors and the speakers which did current sensing and the like which would disconnect the outputs. Note that this is different from the RC network used to prevent oscillation at high frequencies, which is still often used.
As the reply in the thread above notes, thats not the same thing as leaving the speaker completely naked to amplifier malfunctions. Fuses on the rails, DC sensing / DC bias adjusting circuits can all be in the amp without being what we used to call speaker protection circuits.
Should also point out that it’s not uncommon for an amp to have a relay at the outputs. My Luxman integrated had such a relay which mutes the outputs until it stabilizes on. Quite handy and much maligned.
Also, a number of high end speaker makers have stopped using protection circuitry inside the speakers themselves. Honestly of the two this is the one that should be forever purged from consumer devices. Amps with output relays and appropriate sensors however are good.