really it depends on the technology in the scan convertors whether they can handle this.

it isnt just macs - this affects pc's as well.
the so called '75hz' output from the boards isnt exactly 75hz.

and its different at different screen sizes.
at 800x600 its different from 1024x768 and different again at 1280x1024.

you will probably have to test different scan convertors to see how they handle this.
i have used folsom image pro hd's on the last few shows- going to barco d320 screen processors using sdi, and they didnt see this. but they are expensive.