My understanding is there is many caveats to the idea of freezing browser time.

The browser is not designed to work this way and many things such as audio video and some CSS cannot effectively be paused and stepped though.

Is this right or wrong is my information out of date?

very similar to something i released last week: https://webmotion.superhq.ai. especially the "virtual time engine" concept - it is word-to-word similar.