You're probably right. I have one here I've never really tried that hard to use. I got it because so many machines I was getting had broken spool pins, but then ended up with a bunch of spool pins.
The only thing is then there are 2 gaping holes in the top of the machine. I wonder what it would take to "convert" it to the regular spool pin style... hmm,.. I'll have to think on that.
I wonder if it was sold to the person you bought it from as "Heavy Duty" or "Industrial" and someone realized a little too late that it wouldn't do what they wanted and sold it to you.
The manual I take it is the "something like 400 page service manual" for all slants? I'd love to get my hands on a better copy of that one (the pictures are pretty dark), but it's been a life saver as it is.