Now that everything is all back to normal, and I've got a couple of minutes, here's the low-down on the 21st's update
Legacy mode was always only in there is a backup for the circumstance of if the primary application feed went down (since I was not in control of the feed). Due to the nature of the replacement appfeed system, if it goes down then Legacy mode will not work either. Hence the code was pointless.
Now the vast majority of checks, fixes etc are performed by the application feed itself instead of by CA. Net result is that CA now only downloads a single processed file resulting in lower bandwidth and faster initialization.
Previously, CA sent through to dockerMan when installing a template a watered down Overview that wouldn't have had any formatting etc within it. Now, CA sends through the unaltered overview for the user to see when installing a template. Note that the appfeed still applies certain checks to the unaltered overview, and malicious code results in automatic blacklisting.
Hopefully these changes solve the weird case that pops up occasionally of where during an update the apps tab disappears completely.
Now, whether or not you have unRaid checking for plugins, or on whatever frequency you may run it, CA will always let you know if it is out of date. This is grabbed straight from the appfeed itself, so you may see that CA knows that an update is available but the plugins tab shows that there is no update available (trust me: CA is right ) As usual, you can install the update for CA either directly from CA or the plugins tab (after checking for updates).