After I had installed the pigtail for the charger, I hooked it up and went from orange (charging) to green (charged) in less than 2 minutes.
Depending on charger and the battery's state of charge, the behavior can be different. If it is a current Deltran Battery Tender model, then most likely the battery was fully charged. That's good news. However, it's all good to have it plugged in. In practice, it is very difficult to get a lead acid battery to be truly 100% charged. Putting it in float-mode, can help, and should make sulfation lesser of a problem. This could mean less work come charge-capacity recovery time. You can play be ear too. If the battery is healthy and strong, and you don't have any non-stock electrical loads added, and just came back for a long ride, and will be riding again the next day, whether you plug it or not probably won't matter much.
If the charger isn't a Deltran, then the battery may be charged, or the battery may not be charged. Since the battery just came off the alternator, because of the "surface charge", the open-circuit voltage may not be its true reading. After a while, the voltage will come back down to what it should be and the charger will automatically kick in, should the battery not be fully charged.
By charger, I am assuming a smart charger, that's what is being sold these days.