how would they know unless they could prove it through oil analysis? if you follow a routine of maintenance that is recommended by your oil manufacturer with a good high quality filter element......then i believe they would be hard pressed to prove that your oil change regime was the reason for the failure. With Mobil 1, AMSOIL, REDLINE, etc....they are not going to make some outlandish claim and usually will error on side of conservative numbers to be safe.
I have followed my own regime and had engines last 250,000 miles with no issues or problems and still running strong off synthetic oil......this was my Jeep Cherokee I bought in 1994 and sold last year. Everyone else has issues with them but it was my most reliable vehicle to date.