What is the point of SKU codes if they don't actually track inventory across different listings?

Evening from NZ.

I have a challenge that I believe many others will face when using Squarespace's SKU code system.  It is my understanding that a SKU code would be site wide, product listing wide - ie. If an item relating to that SKU code sells out, then other listings on the site including that product and SKU code will also show as out of stock.

Example...

I sell plants with pots.

I also sell pots individually with varying stock levels. When I created these listings there were SKU codes created - I thought this was great!

However, the issue arises when Customer A wants to order a cactus plant with a "Blue" pot from the variant options of which there is ONE "Blue" pot left in my storeroom. They complete the purchase.

Customer B comes along and wants to order a different plant from and also wants a "Blue" pot variant - if the SKU codes worked as they should then Customer B should be able to see that "Blue" is unavailable as a variant because Customer A purchased the last one in stock.

I was told by CC that I need to manually keep stock of each item in this case - which would mean a lot of time spent checking and updating listings to reflect pot colours sold.
Which is why SKU codes are so important!

Can anyone help me with this? Or has anyone else experienced this and found a work around that helps?

Thank you,

Katrina