I have a Low-G tenor. I think it's mainly a tenor thing because the larger body really makes the bass-iness of the Low-G stand out. You're right, I've only heard it talked about on a tenor (or maybe a super-concert).
I'm no authority but I'm guessing the reason the rajao (from which I've read the uke derived its tuning) was tuned reentrant in the first place was because they felt low pitched strings didn't couple so well acoustically with the small body size. A larger instrument like a tenor uke would have less of a problem along those lines. But take that with a grain of salt, coming from me...
As a builder, I'd go along with that, and to further expand that, the ukes we build in my "Build a Uke in Four Days" course are soprano pineapples, and they sound really good up in "D" tuning with a re-entrant "A". They sound bright, happy, and really trad.
I have a low G on my long neck soprano. It is a non-wound Worth Low G. It works pretty well on that concert length neck, but the low G on the Tenor Neck sounds better. I think it is the combination of the longer scale and the soundbox size being better suited to low notes. Think of the size of a stand up bass or cello. Long strings, big body = nice low notes. Hard to fight physics.
In my experience, a string that is too thick for it's length will give a deadened sound.
It does seem most common on tenor. It extends melodic range. I tried Worth brown low g strings on my pono tenor, but switched back to high g. I recently bought a set of Aquila wound low g sopranos. I just have to decide which soprano to try them on and go for it.
Regards,
Ray