A big issue of overtones in this one: it’s not only telling you a term is used, but usually implying that it’s incorrect. A so-called expert or a so-called friend, for example, is not to be trusted!
Dutch can at times do that too, more with zogenaamd and zogeheten than with zogenoemd, used adverbially rather than as an adjective (Hij was zogenaamd ziek). Examples:
- so-called hydroxychloroquine => known as hydroxychloroquine
(no: it really is called hydroxychloroquine)
- so-called Service Provider => referred to as the Service Provider
(no: they really are providing services)
- so-called intelligent solutions => solutions we call “intelligent”
(no: we really do think the solutions are intelligent)
Usage in the neutral sense is certainly increasing, in American English in particular, so it isn’t a gross error. But it’s probably best never to use so-called unless you’re deliberately making insinuations. There are always alternatives, as shown above.
Prevalence: high. A good way of implying (without saying) an unintended extra meaning.
Frequency: endemic. Dutch writers will rarely use anything other than so-called for the three terms listed above.
Native: sometimes. One of those lazy ones that you’re taught at school but tend to forget in everyday speech.