Right now ConvertKit's Commerce options for selling digital products are fairly limited - the folks you talked to are correct in that it doesn't allow you to sell multiple items on one form, or to create several options for a single item. I would expect ConvertKit to enhance things in the future with updates, but right now the service is fairly basic. Zapier is a great way to connect ConvertKit to other services so you could use their sales functionality, then feed the purchaser's information to your ConvertKit account for your ongoing marketing and future sales.

Aaron HockleyCommunity Guru
Photographer, Writer, Consultant