It seems you are assuming that because the majority of people have a certain quantity of glutamate receptors, that they are the healthy ones and that we should be trying to bring autistic people up to that level. Is that right?

Why not consider the opposite, that the most beneficial quantity of glutamate receptors could be somewhere below the typical amount? If that were true, then we could try to help others reduce their glutamate receptor level to become healthier and more successful (and a little more autistic).

If we found, say, an association between a lower level of neurological characteristic X and concert-level piano skill, then those who aspire to play that instrument at an elite level might try to decrease X. The fact that most of us are rubbish piano players would not be evidence that lower levels of X are harmful, but very much the opposite.