i think he said it because you're tires would be rubbing the inside of the wheel well
I have about 2.5 - 3 inches between my 17" rims and my wheel wells.
The tires are equal in width, so that shouldn't be a problem. the rim offset is the same since it's the same rim only bigger.
And I have more than enough spave between my wheels and wells (see pic)
There must be celi's with 19's out there, right?