This is weird, but not only does my 2006 V6 EX-L have a separate A/C on/off button, but every other Honda I've owned (nearly a dozen) going back to my Gen #1 1980 Accord Sedan with its dealer-installed A/C has had a separate A/C on/off switch. I find it strange that the current VP would not offer that functionality.
And I agree there should be some way to defeat the A/C auto-on with defrost altho 99 times out of 100 it would be better to have it on. I don't want some faceless engineers or some computer deciding what's best for me when a simple on/off defeat functionality is not only entirely possible, but is present on every other model in the line-up.