[TeMPOraL]

> as long as you don't break the UX contracts (i.e. browser history is left unchanged and page state under modal is remembered) does it matter how you achieve the modal-like behaviour?

I feel like the hazard here is that many developers don't know, care about, or care about knowing, the full extent of the UX contract, and as a result implement something that's only halfway there.

My go-to example of this is one of the Java UI toolkit of old, which reimplemented all controls but tried to make them look as if they were native. The end result was a set of controls that kind-of looked like native ones, except they didn't support appropriate context menus and less-known keyboard shortcuts.