See https://bugzilla.redhat.com/show_bug.cgi?id=600543, an excerpt:

"...the more I thought about this and discussed with others this sort of snowballed into a discussion of why plugin config updates are synchronous, and group updates sequential, as opposed to asynch and parallel.  From discussions with jmarques it seems the reason for the synchronous approach may no longer apply, in short it was done for gui limitations and user experience reasons.

So, my recommendation here is that we change plugin config update to be
asynch, and as such change the impl to mirror resource config updates,
marshalled with timeout logic applied by quartz jobs.

Making this change will prevent us from needing to do some fairly complex work
to properly solve this issue [600543], which would entail some questionable timeout logic (hard to guess what it should be given the sequential application to N resources), or possibly individual quartz jobs for each update.  There are
server shutdown/crash/HA issues that make some of this non-trivial."


So, in short, with newer gui capabilities, like in place updates, I think we should make this change to both speed up group plugin config update by making it parallel and simplify our (group) config update logic by making plugin and resource config update handling analogous.