Not so, at least for Selmer. I have Selmer horns (Series 9, Series 9*, Series 10S) that come in the following configurations:
Fork Eb only (Selmer Series 9* in A)
"Full Boehm" with fork Eb, articulated G# with extra trill key, LH Eb lever and low Eb key (Selmer Series 9 in A and Bb)
Partial "full Boehm" with fork Eb, articulated G# with extra trill key, LH Eb lever (Selmer Series 10S)
Articulated G# with extra trill key only (Selmer Series 9)
In addition, I have a very tarnished and slightly damaged Selmer metal clarinet with articulated G# with extra trill key and fork Eb only.
Back in the day when I bought my "matched pair of orchestral clarinets, I was given the choice of any or all of these mechanisms. Similarly, I know that Heckel sold their Boehm horns in a variety of such configurations.
Sadly, those days are long gone. Although Buffet has a list that says that you can purchase your Buffet horn in these different configurations, I've never actually seen a Buffet soprano with anything beyond the LH Eb lever. Amati still sells a "full Boehm", and I would imagine that Rossi and other makers would be willing to offer you the same (for a very pretty premium price). But Selmer (and, even more strangely, Leblanc, which used to offer a "near "full Boehm" in their Pete Fountain model) seem to have gotten out of the business entirely.
Fork Eb only (Selmer Series 9* in A)
"Full Boehm" with fork Eb, articulated G# with extra trill key, LH Eb lever and low Eb key (Selmer Series 9 in A and Bb)
Partial "full Boehm" with fork Eb, articulated G# with extra trill key, LH Eb lever (Selmer Series 10S)
Articulated G# with extra trill key only (Selmer Series 9)
In addition, I have a very tarnished and slightly damaged Selmer metal clarinet with articulated G# with extra trill key and fork Eb only.
Back in the day when I bought my "matched pair of orchestral clarinets, I was given the choice of any or all of these mechanisms. Similarly, I know that Heckel sold their Boehm horns in a variety of such configurations.
Sadly, those days are long gone. Although Buffet has a list that says that you can purchase your Buffet horn in these different configurations, I've never actually seen a Buffet soprano with anything beyond the LH Eb lever. Amati still sells a "full Boehm", and I would imagine that Rossi and other makers would be willing to offer you the same (for a very pretty premium price). But Selmer (and, even more strangely, Leblanc, which used to offer a "near "full Boehm" in their Pete Fountain model) seem to have gotten out of the business entirely.