This is also one of the reasons they claim you can tell stitch quality differences between an industrial and a domestic.
My personal opinion also is that plastic parts vs. metal makes a slight difference in tolerance in the machine and it comes out on the stitches, assuming all is working and adjusted in the machine. Also thread makes a difference in the slant: modern spools have the thread wound different and comes off the spool different then vintage spools. Modernly, industrial spools work the same as the vintage ones do.
Saying that, I use domestics. Generally I use an industrial thread holder attached to my table where the spool is not on the machine at all, or I use a mug and wire behind the machine, spool on the machine when I wind it myself (usually wooden spools).
My 66 treadle (1928) is perfectly straight stitches if I use thread I have wound myself or industrial cones. If I use a tool to make modern spools work, it's 1/32 slant.
My Davis evenfeed slants 1/64 regardless of thread.
My 99 (1940) slants 1/16 with modern spools, 1/32 industrial.
My 201 slants 1/32 with modern spools, 1/64 with those I wind myself and none with industrial spools.
My featherweight (1938) slants 1/64 with self wound and industrial, 1/16 with modern.
My Pfaff I have for zig zag is a huge whatever. It slants 1/16-1/64 depending on BRAND of thread. Worse with Gutermann.
All of these are metal mechanical machines.