to piggy back off this - What will rate limits look like for shops with over 50k variations with 1k
Specifically:
The following Admin API resources, in both GraphQL and REST versions, have an additional throttle that takes effect when a store has 50,000 product variants. After this threshold is reached, no more than 1,000 new variants can be created per day.
https://shopify.dev/docs/api/usage/rate-limits#resource-based-rate-limits
This is very easy to do and most of my customers run in to this issue almost everyday and we have to reference this article to them.