Re-mastered LP question

Was this first LP pre-RIAA?

The reason for going to the RIAA standard was to allow for more bass in recordings.
Since bass notes require more groove space the RIAA curve was developed. Your phono-stage compensates for the the reduced bass frequencies actually recorded into the groove by boosting them when the LP is being played.

Without the deep bass on the LP anymore it doesn't take as much space to record the same music.

Or maybe I'm wrong about all of this.

Perhaps the cutter lathe technology has improved allowing the grooves to be placed closer together.

Although what Twl says is generally true, that (compression) is clearly not the case with the Classic reissue, which is superior in terms of dynamics and resolution of ambient detail than (though not as warm as) the original issue, as we found in a comparison in my system. I'm curious as to why the grooves are closer together myself; perhaps an inquiry of Mike Hobson might give an answer.

Not sure about that particular LP, but some of the older LPs like that had wider groove spacing to allow for more dynamics. It is possible that the remaster had some compression applied to allow for closer groove spacing. This was quite common in the Dynagroove series.