max SPL numbers are always pretty much wishful thinking.
Max SPL numbers can mean VERY different things, and are often not what the user can actually get out of them.
1: Is the "Max SPL" some sort of average max-or a single peak in the response that gives a peak, but the overall level is lower?
I have seen this on quite a few products, and sometimes that "peak" in the response is 10dB louder than what the rest of the response can actually do.
On one particular sub model that peak is actually at 1,800 Hz. Not exactly in the sub range-----------
HOWEVER-the cabinet CAN produce that peak so they are not lying, but they are NOT telling the user the "truth" as they would like it to be told to them.
2: The other peak is simply the maximum level on a short duration signal. This is simply a misunderstanding of the user-not the manufacturer.
The problem is that normal SPL meters cannot read that peak (the integration time of the meter is to slow/long), so the user "thinks" that the speaker is not producing the level the spec sheet says.
YES the speaker is-but YOU don't have the proper tools to read it. You need a PEAK response SPL meter (not fast or max). The cheap meters simply are to slow.
3: Another is "What does it sound like at that SPL?". In many cases the loudspeaker CAN produce a particular SPL, but it sounds so bad you don't want to listen to it at that SPL.
Currently we don't have a spec of "Maximum listenable SPL".
That would be a VERY interesting spec and to see how it is applied, if it ever happens-I doubt it.
If you have a good peak reading SPL meter, you can measure the same signal at the same location, and get measurements that are 30dB or more different.
They are all correct-for the particular weighting and time applied to them.
Loudness is NOT a simple thing