I don't find this to be surprising at all. In order to provide a slide that is an immediate "insert and play" slide on any horn, it would have to be made with tolerances that would be much too loose on a number of horns. The slide is likely to need at least some lapping and MAY need some mild alignment to fit a particular instrument. This is all very simple and any reasonable repair tech should be able to do it in a few minutes at very little cost.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)