You have misunderstood their following response

To answer your question, no, you do not need to have Advanced Inventory enabled to turn on Enhanced Inventory Receiving (EIR) in QuickBooks Desktop. EIR is a separate feature that can be enabled independently of Advanced Inventory.

You can see there are 2 different buttons to enable the Advanced Inventory feature and the EIR feature. You need to have Enterprise Platinum to enable either of those features. That's why their Support staff asks you to contact Sales since you have the Silver or Gold edition.