what's going on with specs?

Of the 4 amps the OP mentions maybe and that's a long shot maybe one might pick out the BHK 250 over the other 3 between the other 3 I know I wouldn't be able too.

so close you would have a hard time telling them apart better than guessing

Perhaps some might be guessing, but there are innumerable people who can tell the difference on any program.

In firearms, there a units whose accuracy is so good that they are set aside for competition. These arms may be designated 1:100 or 1:1000 depending on their superiority.

The same is true for many manufactured item: Engines, binoculars, electronics, etc. Manufacturers run Monte Carlo analysis based on component part tolerances. Just as there are 1:100 on the top, there will be the same on the bottom. They meet spec, but will never hold.

I once bought an amp a pal owned based on how it sounded in both our systems. After a couple of weeks, I returned the one I bought as it was sonically inferior. On the bench, both measured the same.

When we shipped systems for recording studios, the final QC was a listening test. Some units were reworked, some binned.

The biggest variable in the determination of how good something sounds when listening to reproduced or actual live music is the human auditory system. Thus, it is not true that 2 amplifiers that measure the same will sound identical, even if they are listened to at different times by the same human. This fallacy is sometimes repeated by engineers but never would never be uttered by a neuroscientist who understands the complexity of the human auditory system.

Preference of sound is not the point. Whether one thinks certain products that reproduce music or if a live event sounds "good" is subjective. If one thinks amp A sounds better than amp B buy amp A but If an amplifiers noise and distortion are measured to be beyond human hearing then that component is considered neutral or transparent, it neither adds or subtracts from the signal sent. If 2 amplifiers measure the same and are considered transparent then they will sound the same or so close they can't be differentiated in a blind test. The test can be one day or 2 days or 10 days, months apart. If one can successfully pick one over the other better than chance no matter how many times they listen then the amps either don't measure the same or the test is flawed.