This must be a related problem.
Attempting to resize layout columns doesn't appear to work. I began with a 67% : 33% layout and attempted to convert it to 60%:40%. I removed the SItefinity _67 and _33 classes on the columns. Below are the screenshots to the same layout.
Once again, the preview page looks correct. (However it's still not because now the columns aren't being floated so they're stacking. But let's ignore that because I see my width changes):
Once again, here is the published page, which is not correct:
Another import thing to note is that this is a completely different Sitefinity installation than what I wrote about in the previous post. Same issue. Changes do not take effect, but looks correct in the preview.