Thanks for the suggestion, but

(a) I don't think it's worth making this change.
(b) Your change still won't do the right thing in all cases.
(c) Your approach (of passing a parameter just for this) doesn't feel right.

For example, what if pyvenv is invoked using a symlink such as pyvenv-3.4? Your code would say "pyvenv", which seems "just as wrong" as saying "venv".

I don't believe the current state of affairs is really confusing (it hasn't been brought up before) - and even if it is, the right fix seems to be to mention in the documentation that the usage statement may vary slightly depending on exactly how the venv functionality is invoked.