SO what profile do you have on YOUR 19's??
My rims are 19x8 all round. My tyre profile is 245/35/19, and this has a 1inch bigger rolling diametre than std wheels. So to put his (and your) theories into math; after doing a few simple calculation, you will need to have the following profile to have the same rolling diametre: 245/25/19.
Are tyres available with a 245/25/19 profile? And who will want to pay hundreds more dollars for such a specific profile with very hard "ride" characteristics?
So once again i ask: Do you, or the other person, have experience with wheels and tyres? If not, do you really know what you are talkin about?
I have no "work experience" with wheels and tyres, but have had my 19's for about 2.5yrs and did alot of research and asked, the experts/fitters, alot of questions.