The naming of the long fast inserters is confusing. I expect Fast inserter IV to be faster than Fast inserter III, which would be faster than Fast inserter II, which would be faster than vanilla Fast inserter. But their rotation speed goes down while their handles get longer. When you hover over them, there is no indication that they have longer handles. So, they look like there is a bug.

My suggestion is to change their names and descriptions to include info about the extra length. Perhaps name them Long fast inserter, Longer fast inserter, Longest fast inserter. That shows people that their length increases, not their speed. Though, I'm not sure if other languages have long/longer/longest word versions.

The mod summary, information page, and FAQ page are all mentioning this mod is about inserters of "longer reach" quite clearly.
If you ever scroll to see this mod page to see the screenshots and tables, you will quickly realize they are all about inserters of extending ranges.
Especially before the integrated series come into play, there is not a single word about speed.
I have no idea how you get the impression they would be about higher speed.

If you want higher inserter speeds, you should go for the four integrated series. I do not make yet-another inserter series that are also targeting for higher speeds.

I did read all of that today -- and a bunch of information on many of your mods. (I'm exploring a bunch of them of the first time.) I could not remember everything that I read. I was going by what appear in-game, which is what lead to my confusion.

I'm not looking for higher inserter speeds. Perhaps I am the one making things confusing. (I seem to be good at that.) Thank you for reading my comment. I can always change the entity names myself. Have a good day.