It sounds like the printer has developed a workflow that is consistent for them. ...Their special recipe of perfection, so to speak. orrrrrrrrrrr
I am not the end user in question here. A customer call me for support and stated he must print all spots at angle 25. He would not accept 22.5. This confused me.
:ROFLMAO: Don't let that confuse you. If the printer is reading the same Fresner book you are --- and they think Scott is the messiah of screen printing, go with the 25 line screen. Those types typically won't stop drinking the Kool-Aid. It's just a cult thing --- give 'em a bone.
As far as the same angle for the separations, in my experience, the issues I've found with getting a successful print are based more on avoiding a screen mesh moire than one caused by the layers of ink.
Admittedly, it's been a while since I've printed, but the theory at the time was that one would be physically mixing inks on the shirt by printing wet-on-wet. The dot would get mashed and no moire would be visible by the end of the print sequence --- especially if one printed a final highlight white for
lots of dot mash.
...Also, during separation I would guess you need to ensure that no two colors have the same density at the same location - otherwise your dots would land directly on top of each other.
Personally, I hate shirts that look faded after one washing. IMO, the greater the density the better the result. If there is not much ink density, the fibers of the shirt peek through, and around, sparse halftone dots. This fibrillation makes the garment look old, fast. The more ink, the more it will physically mix on the shirt for a thicker coating of color. ...of course, that's a constraint of the design and based on the number of colors printing.
Because it's simulated process, that implies that it's four our more colors printing and mashing to get the desired look. For simple spot color printing with halftones --- where only a couple colors overlap --- I would be inclined to print with the separations at the more traditional rotations.
Just my .o2