This has been happening for years and years. Dealers ALWAYS do it for a few extra bucks. For two reasons - Extra cash as they list it on their site, and so that you are discouraged from doing your own repairs.
In the mid 90's, a "well known" dealer STOLE a manual out of a machine that was in their workshop. My friend took his KISS, which was STILL under warranty and they swapped out a poorer playfield AND stole the original manual out of his game. I found it in their display cabinet. When I prompted them, they lied, but I knew it came out of the KISS because the operator's stamp was inside the game and on the manual with a serial number. They had it for sale for $60.
Nowadays, the practice of removing the manuals is commonplace. They are no longer reprinted, so why are they on Dealer's websites ? This practice really annoys the crap out of me.