I don't believe it's the individual actions themselves that is versioned but rather the collection of install actions.  Thus if you update a bundles name, icon, etc. and give it a new version the installs do not run again unless you alter an install action.  Sometimes it is necessary to do a dummy edit on an install action to get them to run again.  I've never had to actually "dummy edit" every single install action to get them to run again.   (Under the Hood I can't say if each action has a version # or the Set has the Version#, but it operates as a "Set" so that any change to the set will cause everything to run again.)

Getting the behavior to make the changes would require updating the GUI and exposing additional options because quite often the desire is to re-run everything so there would need to be an ability for finer control.  That would be useful but an RFE.  At this point, you would need to use "Action Level Sys Reqs" to skip actions you don't want to run again.  You could check to see if Citrix was installed and the version before calling the MSI or if calling a Citrix Install Bundle I presume the "Bundle is Installed Action" would only run if the current version was old though I personally don't use the "Is Bundle Installed" very often and would need to verify if it checked to see if any version vs current version was installed.  I presume current because that is logical to me but that does not mean it's logical to others or always the best option.

Hmm. I wonder where my brain has this from. Maybe Zen7. ;)
The individual system req to check if a bundle is installed is an interesting idea. I originally thought that won't work as you can't check the same bundle you're just installing, but this isn't the case here.
I'll test this...