Well, that partition was not created and Í imagine instead its content overwrote the recovery partition.Upgrade does add a partition between the Original recovery partition and the Windows Partition that contains the W10 equivalent of Win Re Tools partition. Basically it cuts 450MB off the Windows partition to make the new W10 Tools partition.
How much free space did you have on C: when you started?
What was te reason, I can't say.
Also, I've not checked C: free space