They're similar, yes, but they're not the same.
The white papers for the
R series and
LS50 Meta are available, and they've discussed the changes.
They're not huge fundamental changes - they call the Uni-Qs "12th generation" and "12th generation with MAT" respectively, and they're at roughly the same price point (unlike some other drivers of the same generation).
The LS50 Meta did start from the R series driver, incorporating stuff it introduced like the new higher-flux midrange magnet system, and the tweeter gap damper.
It's not super clear, cos the LS50 Meta paper is mainly making comparisons with the
original LS50, so repeats some of the stuff seen in the R series paper.
But the main differences seem to be:
1) A bit bigger and with a Z-flex surround to assist 2-way operation (a fundamental design difference common with the LS50, rather than an update)
2) Wider tweeter duct to support the MAT, and the MAT itself.
3) Reimplemented tweeter gap damper because of wider duct. (It wasn't present at all in the original LS50, being new in R series). No information which version actually performs better.
4) Stiffened tangerine waveguide
5) Reworked tweeter magnet + coil system
6) Larger aluminium shorting rings doing whatever they do in the midrange magnets
But I wouldn't sweat it that much. People get hung up on the Uni-Q "versions", but the actual price levels - Q / R+LS / Reference / Blade - are more significant. R series and LS50 Meta are in the same price bracket, and not massively different in version.
And being 3-way rather than 2-way is a significant overall advantage for the R series. LS50 gives you more "point source" Uni-Q goodness, but it's at a low-end distortion cost.