Looking at Denniston I see Vals Cruzada and she adds that even in the Golden Age some still danced Viennese Waltz in some parts of BA.
(tuns out that one "pattern" we learned at ATUSA was doing crosses to waltz timing but don't remember hearing it called that)
Other than that, criollo would be a local adaptation of something foreign, no?
Well, yes, they would, wouldn't they? Viennese Waltz has a much longer history. Known around Vienna in the mid 18th century (as a local folk dance,
Ländler, danced in the Tirol and Bavaria), so comparable age to your country, and very popular in Vienna in the late 18th and early 19th century (see also the composed music by Strauss, etc, in that era). Codified as an American standard dance sometime in the 19th century.
Argentine Tango Vals (picking up the various language terms used by immigrants - Walz (German - to roll, or revolve), Vals (Scandinavian), Valse (French). Although there are earlier references to Vals criollo, it became better known around the mid 1930's (Golden Age), with most music composed in that era. The music, although related to Viennese Waltz, is different. Vals music is generally faster. The dance had evolved from those earlier waltzes, including the Viennese Waltz, brought over by immigrants and mixed with other dances. It's a fusion dance! So yes, of course there were people dancing Viennese Waltz to the music at that time.
one "pattern" we learned at ATUSA was doing crosses to waltz timing
If you learned AT with sequences like the 8CB, then that didn't come in until the 1930's (the 'cross' is much earlier! The 8CB was just a pattern for learning elements). Perhaps because we didn't learn the 8CB 'pattern' until later our early vals was always about revolving, or rotating, with 'rock steps', giros and ochos, cross-system - and, of course, timing and musicality. And progressing!
So, as a fusion dance, I go back to Argentine Tango Vals.