So you can do squadron transits. Jump tenders can only do standard transits, which are suicide if the jump is going to be contested at all. You don't need one on every ship, but you do need them on some ships. Probably 1 jump ship to every 3-5 other ships, depending on your squad jump tech.
A jump tender is usually meant by a ship that is more of a support ship than a combat ship, their role are mainly to jump other ships and then support in a none combat way. That is what we normally refer to as jump tender, at least I do. A jump capable ship of a squadron leader is a ship that is a dedicated part of a specific squadron of ships and manoeuvre with it... at least that is how I use those terms.
A jump tender can be used to squadron jump ships equally well as you can with a jump capable squadron leader. Often, Jump tenders, can even jump a greater number of ships too, depending on how you design them. But I always give my "Jump Tenders" max squadron size jump engines. Also a jump tender don't have to be as big as the ship they are jumping anymore either. So if you have a bunch of 100kt ships and you don't need to build a 100kt ship to jump it... you can have a much smaller less capable ship whose only job is to provide one or more of such ships jump capabilities and then provide some fuel, ammunition, supplies, perhaps a hangar with some sensor scout, rescue shuttles, cryo pods for storing rescued crew, boarding troops and shuttles for transporting them or what have you.
Do you have enough jump tenders to jump all of your ships at once, that is a different question. I usually don't believe that you need the capability to jump your entire fleet of capital ships at the same time, that is probably overkill in terms of jump capability for the most part.
In C# I believe you even can use Jump Tender Stations to jump ships and even they can use squadron jumps. That means you can potentially use commercial support ships to tractor your Jump Gates/Stations and place them on a jump point and help military ships squadron jump. Could be a cheap way to give a large number of ships jump capabilities as you rarely need jump capability for every ship in a fleet usually. These Jump Tender Stations also can be commercial and so is both cheaper and easier to maintain and you can have them sit at jump points indefinitely.