How does BYOB work?
By default, BYOB uses variants to adjust the bundle price. When a customer builds a bundle, a variant is created with a suitable price and weight. For each product, there are only 100 variants under the Shopify limit. When the 100 variants in a product are used up, a new product is created. Think of each variant as a note to record selected items.
For example, to select 4 items from 20, there are more than 20^4, i.e 160,000 combinations. The combinations can never be stored with 100 variants.
If you don't like these dummy variants, you can pair a bundle with a discount code where the items are added to the cart separately. But it's less flexible than the default mode.
For more info, please refer to this article to see how it works: Get started with BYOB