Is it no longer possible to have amazon spread out inventory to multiple FCs for small shipments?

For small shipments (say 45 units, 1 cartoon), Amazon use to spread this out across the country. Now I don’t see the option and all my inventory is stuck in a single FC and shipping times to customers are horrendous.

This is a big issue for us since when testing a new product, we can’t get accurate results. Customers aren’t going to buy a product with 8-9 day a shipping. Which makes PPC perform terrible, etc. And we aren’t going to send a large shipment for a new product we are testing (all our products are homemade)

Am I missing something here?