Blocks: Hiding vs overwriting saved content

I noticed that in some blocks we replace the saved version of the blocks with a server side render (e.g. Calendly and OpenTable) whereas in others we append the server side render to the saved version and then hide the saved version (e.g. Eventbrite).

Is there a reason for taking one approach vs the other?

Compare the Calendly, OpenTable, and Eventbrite block implementations to trace how each handles saved content and server-side rendering. Determine whether the different approaches are intentional, then record the rationale and expected behavior for each block so the inconsistency is explained or a follow-up change can be scoped.

Written by the indexing model from the issue text.