Microsoft long ago lost the muscle to "demand" that a certain version of
one of their operating systems be installed on a computer.
I'd think differently. All they have to say is - previous version(s) is
discontinued. After all, it's their products and they can determine when
and for how long to supply it.
Obviously, it will include more considerations into when to discontinue a
product, but to say it has no "influence" on how OEMs to carry which OS, it
is not likely the case.
Of course, one can also say that OEMs have a choice for not carrying Windows
at all, but we all know that it's impossible under the current market
condition.
They are more cautiously using their muscle now but it is there and will be
there for many years.