Lectora Inspire is the package that contains all of these extras.
Depending on when you purchased it, Inspire may have also had other benefits as well. For example, at least for my company, at the time we first purchased Lectora Inspire (and have since had a continuous maintenance package), we also got more slots for uploading content on ReviewLink than if you were to purchase Inspire today – according to the page listing features of Inspire, I believe it mentions Inspire currently entitles you to 50 slots for uploaded content on ReviewLink.
The cost of purchasing Lectora Publisher + ReviewLink’s unlimited upload package is about what it would be to just get Inspire, which is probably why many just get Inspire if they know they’ll want to use ReviewLink. And of course none of this includes the cost of the maintenance plan.
I don’t know what the default number of items you can upload to ReviewLink for Publisher is though, so as of today it might be better to just do that like you said, if you don’t need/want the rest and the amount of ReviewLink slots are sufficient.