Publix Supermarkets: get check 6 months after cashing out, was told that keeping it in stock not an option

I seperated from publix on X date and cashed the entirety of the stock in my account.
I recieved the total sum of what I had in my account.
Now, half a year later, I recieve a check for a couple grand.
They stated that it was stock owed from the last quarter that I had worked before I quit. (If publix does stock by quarters, why am I getting this 6 months later?)
They also stated that they were basing this from a document that I had signed 6 months previous to clear the account, and that I have no option to keep the “earned stock” in actual stock, rather I must take the check.

I was told that I must cash this check, or lose the money.
I'm confused why I'm being forced to cash a check instead of being offered an option to keep the “earned stock” in the employee sharehold. It seems like odd timing now that publix is having a 5/1 split.

Can someone please explain this to me? I am not super familiar with stocks, but this doesn't sit right with me.