This is a great question! IMHO All Spey casts are necessary learning. They will make you a better fisherman in the end no matter the situation and will allow different presentations in more difficult settings no matter if its a single hand, double hand, or switch rod. The most important thing when learning to cast a switch rod is lining it for the way you want to fish. The nature of most switch rods is to be a bit faster action the most Spey rods and since they are shorter they tend to not be as "feely" as a Spey rod so they tend to be harder to develop timing for a beginning Spey caster, but don't let this dissuade you. To help regain feel it is just more imperative to line it correctly with a line that promotes the type of fishing you want to do. If you plan on fishing deep with heaver sink tips and larger weighted flies I would recommend getting an Airflo Skagit Switch line and 10' of t11 to start this will be for sustained anchor casting mostly then you will only need to learn the Snap T, Skagit Double, and Perry Poke (see Ed Ward and Skagit Master 1) from both sides of your body and you will be fishing before you know it. If you are wanting to fish a dry line with surface patterns, or wet/damp Spey and Dee style flies and would like the option to throw a little bigger patterns with not nearly as much weight as a Super Intruder then the Rio Scandi Short Versi-Tip is the way to go. This line gives the freedom to do about anything with it won't fish as deep as the Airflo Skagit Switch head, but it can still toss decent sized flies. The Rio SSV line is capable of all types of casts both airborne and waterborne anchor casts. The you have the opportunity to learn not only the Snap T and Double Spey, but the Single Spey and Snake Roll casts as well. His line allows for the caster to aerialize the entire head and tip easily for anchor placement then rocket it out there. If you are looking to fish nymphs under a bobber (indicator) with your switch rod then you need to get a line designed especially for that i.e. either the Airflo Speydicator or the Rio Switch lines. With either of these lines they aren't really designed to be great Spey casting lines but more or less to turn over a lot of wind resistant material at moderate distances with some type of roll cast. They cast I use the most with this type of line is the double Spey because it keeps the leader in the water for the setup helping to eliminate tangles and wind interference. I consider either of these lines as plopper lines. Meaning you just need to get the flies out and down and get a drift going "just plop it out there" when I fish a switch rod from a boat I use the Speydicator line and find myself casting it overhead with a big open loop (limit the amount of false casts) from time to time. So in short for me there is no definite answer, but since a switch rod can be harder to develop casting feel for get a line that is designed to fish the way you want to and then be patient with yourself as you learn to cast you will be rocking it before you know it.
For what it's worth,
Mc