Braslvr, I have a feeling our recipes are related. The line "Do NOT add any sugar or anything with sugar in it!" is the giveaway.
(Mine might be a little older, as the mustard powder was probably swapped for prepared mustard during the step-saving 60s and 70s. )

I'd be curious to see what you think of the finished product if you put the salad together when the potatoes are still warm. I find they absorb more that way, though it could just be old school thinking.

And notsosmart, the secret ingredient in mine is the celery seed. It's a flavor that you don't realize is missing from a lot of prepared ones until you taste a salad with it. The same chef who suggested adding a baker for texture also said you can sometimes get away with storebought potato salad if you mix in some celery seed and vinegar (to cut the sweetness of some prepared ones) and/or toss in some dill pickles.

Dill can also be a fine addition.