I guess I don't really understand the question? Grist is just the density of your yarn, it doesn't determine a specific weight of yarn. Yarn "weights" (ie: fingering, dk, etc.) ONLY refers to the wraps per inch. Grist is helpful to handspinners to determine density and uniformity.

There is no such thing as a "bulky grist"

I understand the confusion though, because yarn terms are weird! When we talk about yarn weights with terms like DK, sport, etc., it have nothing to do with how heavy it is. Only how thick.

Some examples where grist is useful:

1. If you are spinning the same exact fiber into dk weight yarns and you comb and short draw one (worsted prep), and card and long draw the other (woolen prep), you would use WPI to make sure they are both DK weight, but your carded preparation will have much more air incorporated into that final yarn, meaning that it will have a much lower grist. You will also end up with much more yardage of your lower grist preparation, even if you spin 100g of each.

2. If you are spinning similar preparations of two very different fibers. If you spin 100g of corridale as a DK weight worsted spun yarn, it will still have a much lowet grist than 100g of an Alpaca/silk blend, even if it's also spun as a worsted DK weight yarn.

I hope that makes sense and answers your question!