My TV is 60Hz 720p LCD but what does that matter? You've just admitted that they run at 50Hz, which is the entire issue.
No noticeable slowdown? Simple math tells me you and your testers are completely wrong. The games are programmed to run at 60 frames per second because they're NTSC-US releases, but they're being forced to run at 50 frames per second by whatever SCEE have done to them. The end result of this is that they run a sixth slower than they should and this is blatantly obvious. Music, video and gameplay are all noticeably slower, solely because of this issue. And if you'd like to know what kind of effect this has, well for every six hours of gameplay played at normal speed (60Hz), an entire hour is added when running at 50Hz. Or in other words, if it took you six hours to reach a spot in the normal version, it'd take you 7 hours to reach the same spot in the version SCEE have released.
The fact that SCEE is trying to shrug this off as a non-issue and lie about there being no difference is disgusting. You're purposefully releasing games that are inferior to their original releases, unlike Nintendo, who've released import titles that actually run properly.
And as for the description, well seeing as I bought those games when they were being advertised as 60Hz, it's still as false advertising regardless of whatever changes you make now.
Fix them so that they run properly or give me a refund. Simple.