I understand that while consistency is important, it's not the only thing in operating a weapon. I've never had a problem moving from one system to another after practice. I've never carried Colt revolvers as I don't like the cylinder release direction and rotation of the cylinder compared to S&W. But I have shot enough Colt revolvers to operate the revolver successfully.
I never tried to drop a magazine from a S&W Model 67, confused an 870 12 ga with an AK, or a Cz 75b with a Makarov. Whether I prefer my 75B to the Makarov is not the issue. I can run both successfully because I've practiced with both.
I don't carry firearms defensively without a lot of practice - both the manual-of-arms and plenty of range work.
Familiarity with a variety of guns is good. Practice with a variety of guns is better.
For those who don't practice the manual-of-arms and at the range, sticking with only one gun and one system may be fine, but it doesn't make for a well-rounded and knowledgeable shooter.
There's an old saying, "Nothing is dumber than an expert when you get him off the subject he's an expert in." I've been there and it's true.