[NTG-context] Old-Style numerals command (\os) breaks conversion of hyphens to dashes

[Art Chimes]

I have a fairly large document, 50-60 pp, with lots of numerals,
including hundreds of dates. I wanted to see how it would look with
old-style numbers and I assumed I could bracket the whole text section
of the document within braces and apply the \os command. I didn't turn
out as I expected, however. It did convert the numbers to old-style
digits. But it also unexpectedly changed the em and en dashes back to
hyphens, as they were entered in the source .tex document.

MWE follows below.

I could possibly do a search-and-replace but I am hoping there is a
simpler way to do it.. I am using Libertinus Serif (which does support
old style numerals) and columns, if that matters.  Thank you.

\starttext

First two examples:  Brackets surround text including digits, grouped
hyphens are {\emph not} converted to en and em dashes.

{\os
Ford--Chevy 12345

Chrysler---Plymouth 67890
}
\blank[line]
Next two examples: Brackets surround just the digits, the grouped
hypehns {\emph are} correctly converted to en and em dashes

Honda--Toyota {\os 12345}

Renault---Volkswagen {\os 67890}

\stoptext