Depends on the definition of the term. Timefactor will preserve delay tails when you load a new preset. The only Eventide with completely true spillover (meaning two effects running at once during the changeover) is Space.
The limitations are that for complete spillover, you can only use half the power most of the time to allow double power during changeover. This can lead to weedy effects if you are not careful.
Man, I would kill to have delay and reverb tails during changes. I’d even be thrilled to only have it spill until the input threshold hit a certain point (once I play a note into the new algorithm, kill the tails). Personally, I don’t use the modulation or pitch stuff very often so not having spillover on those wouldn’t bother me, although I know many others do.