Here's a description of Squier Japan instruments...
"Marketing executive Dan Smith, quoted in “The Fender Book” recalled, “Everybody came up to inspect them and the guys almost cried, because the Japanese product was so good — it was what we had been having a hell of a time trying to do.”
If at one time an inexpensive electric guitar was synonymous with a low-quality one, the new Japanese instruments showed that this was no longer the case. In fact, during the late 1980s and early 1990s, it was generally acknowledged that the build quality of Fender instruments made in Japan equaled, or even exceeded their stateside counterparts..."
Regarding the body wood - it's probably sen; a hardwood common to Japan and other Asian countries.
It's similar to ash, but a different species.
Once upon a time, I did some messy pickup routing on my bass (hidden under the pickguard, thankfully).
A few years ago, I cleaned it up by re-routing and filling with a block of alder - which is common on US Fender basses.
That alder was a decent match to the rest of the body, but maybe a little softer.
So IMO the sen body on the MIJ Squiers might split the difference between an ash and alder-bodied bass.
And that's a good thing.