I think PRS still uses the brass infused unobtainium nut on the trem-equipped guitars; my 2021 Special has one, as do my PS guitars with trems.
However, the fixed bridge guitars I currently have all came with bone nuts.
I have a hunch bone nuts are just caving to player's preferences. The composite nut is superior I think, but to the masses it looks like "it has a plastic nut..." which in many players minds equals "cheap".
I'll have to disagree. I don't think it has very much (if anything) to do with the masses and preference for not having plastic.
PRS' early production guitars were trem-equipped, and had composite nuts because they simply work better with a trem. First, the strings glide through them pretty well with less friction than other nuts, so the strings don't get hung up in them as easily as commercially available nuts other brands use. That matters a lot with the very responsive PRS floating trem.
It's important to mention that PRS still puts the composite nuts on all trem equipped models, and the Hollowbody piezo, so if they were catering to the 'I hate plastic' crowd, there'd be no need to do that. I think Paul puts stuff on the guitars he thinks works for what he wants to do with them.
A large segment of the market definitely
wants guitars that sound more like vintage models. Nonetheless, loads and loads of vintage-leaning guitars are made with plastic parts, including large plastic pick guards, for example Custom Shop Fenders, and lots of Gibsons, and people snap them up like candy.
We often hear the phrase, 'greater than the sum of its parts'. Truth is, the parts matter, and taken together do add up to make some of the current PRS models sound more vintage. The bone nut is a small link in that tone chain. Another link is the finish.
Lots of players here have more PRSes than I've had in the past 32 years, but I've had at least 36 that I can think of, starting with a 1991 Custom.
There's no question in my mind that the nitro finished guitars have a subtly different tone than any of the previous poly formulations. The two piece bridge with the current zinc tailpiece instead of aluminum seems to matter a bit, too. By themselves these parts are probably tough to hear, but as I said above, taken together they add up.
Since I still have a vintage Gibson (and have had it since 1967), and owned a lot of vintage gear when it was new gear, I'm familiar with the characteristics of the old guitars. Several of the current PRS models are much
closer to that vintage vibe. Before 2010 or so, PRS was less interested in chasing that vintage tone than they are now, but I think Paul himself has come to appreciate it, and as a customer I certainly do.
I don't mind, or care, if a guitar has plastic on it. It's irrelevant to me, as long as the guitar sounds good. But what PRS is doing with its vintage-style guitars sounds great, and I'm happier with the PRSes I've bought over the last decade, and particularly the nitro PS and Core models I've got. I don't think I'm atypical of the PRS players who appreciate the change in PRS' direction over the last decade.