- Iraqi Jews have it as well.
- In German, the surrounding vernacular, it's rather recent and not at all used in all regions. (It somehow spread from Northern urban French.)
- Davke the Franconian dialects, often seen as the basis for Yiddish, have an apical flapped/trilled r until today. (For that matter, even Southern French varieties retained this, though, on the other hand, some Northern Italian dialects have the uvular r.)
- Most Yidden in Eastern Europe had the uvular r, in spite of the fact that at the time of (their ancestors') emigration from Germany, Germans had the apical, as have the Slavic languages from Polish eastwards, the Baltic languages and coterritorial Eastern German dialects until today.
- Reish can't be "geminated" according to the massoretes, which is (otherwise?) typical of velar and uvular consonants.
The whole thing isn't easy, or, in other words, I'm not simply claiming this was the pronunciation since Môshe Ghabbeinu.
Tidbits: In Russian, the uv. pr. is seen as a Jewish accent, in Czech as aristocratic, in Hungarian as dandyish, in Swedish it's typical of the Southerners, in Italy of the Northeners, whereas the apical r is seen as rural/Southern in French, rural/Southern/Frisian in German, low-prestige/Mizrachi in Ivrit, formal/snobbish/Scotch [sic!] in English.
And: If it isn't the "Parisian" gh fricative, but still a flap/trill, though uvular, many people don't hear the difference! (Try finding a sound clip of Václav Havel.)
Iraqi pronunciation doesn't differentiate between gimel degushe and gimel refuye, but I wonder if at the time they still did, the difference between gh and r was fricative vs. trill. Of course, gh could have been more palatal.
It's still not entirely clear how and where cats produce their purring sound.