Not so. Most came from other multi-engine units, many 'zerstorer' pilots (particularly initial intakes) and later bomber pilots. These men were not only familiar with multi engine aircraft but most held instrument qualifications which were unusual to the point of almost being extinct among late war single engine fighter pilots. Bad weather grounded the Jagdwaffe. There is a clue in the designation of many Me 262 units!
People tend to remember the famous pilots of JG 7 and JV 44, though even there it was by no means all who were 'experten', and imagine all Me 262 units to have been similarly constituted. Many of JG 7s pilots had converted from multi engine types.
In the second half of 1944 the average Luftwaffe single engine fighter pilot still had a total flying time on all types of about 120-130 hours and maybe 10 hours on operational types. What he never got was the on the job training that his allied counterparts got at OTUs and their equivalents. A typical US pilot had a total of around 400 hours, 150 on operational types, before he was posted to a unit where his training would continue. It's a huge and relevant difference.
If you analyse the careers of the Germans shot down during operation Bodenplatte you will find that many had been with their units since October/November 1944 but when shot down on 1st January 1945 had less than five, often one or two, operational missions.
Cheers
Steve
The squadron was formed by Lieutenant General Galland in January 1945. [It was] also known as the "squadron of experts", consisted mainly of volunteers from all Luftwaffe [fighter pilots]. Among them were especially many highly decorated pilots aces, such as
-Gerhard Barkhorn 301 victories
-Herbert Kaiser 68
-Gunther Lützow 110
-Johannes Steinhoff 176
-Heinz Bar 220
-Walter Krupinski. 197
-Walter Roell veteran stuka pilot
-Adolf Galland 104
-Hans-Ekkehard Bob 60
Within the Luftwaffe [it] was jokingly asserted that in this organization the Knights Cross was an essential part of the service uniform.
As they typically managed to get only around 20 to 50 Me 262s into action per day, even if they were not all aces, the aces certainly formed the core of the squadron.