I believe you will be fine, the reason it is often stated, and the reason that they recommend that at Black Widow is simple, compound shooters really open up when due to the let-off feature of the compound when they draw. Traditional bow shooters, are more compressed due to the lack of a let-off, we are hold what we draw from the time we reach anchor to the time we release. This compresses the draw, so it will likely be a little shorter.
I shot nearly two and one half inches longer when I shot compounds than I do with some of my traditional bows. I am one inch shorter with my SAV Black Widow, and two full inches shorter with my PLX and PLA.
With the latter two, I am shooting those bows with a grip that requires that I heel the bow more, a traditional longbow grip of you will. My SAV is shot with a more high wrist grip, similar to when I shot compounds.
I would not worry about the inch difference with your Widow, their bows pack a punch that other bows I have owned even at the same draw weight didn't have.
Congratulations on your new bow.