Not true at all.
It will most definitely decrease further wear on the outer no matter what the problem is! The key word here is "decrease", not that it will no longer have further wear on the outer.
That does not mean, blindly increase pressure without determining if it was a low pressure caused problem when it is as likely an alignment problem, AND, going beyond the spec'd pressure can cause poor traction so it's a bit of a band-aid that creates another issue trying to fix an existing issue, so not a simple "fix" without more specifics considered.
Silly question: Do you drive like a maniac? That will wear the outer edge on the front tires excessively, then even after rotation, you just wear the rotated-to-front, tires outer edge excessively too.
If you don't drive like a maniac, and have rotated them regularly as stated, then it is time for an alignment -OR- look at your suspension components, it could be they are due for replacement BEFORE you do an alignment, not after.