The issue seems to be related with node version I'm using (20.16.0). For some reason, even as I pass hourCycle: 'h12', node was changing it to h11. I tried updating to a newer version of node (v22.15) and the issue "fixed itself" with node not changing from h12 to h11.

I still haven't had the time to see if it was a bug on node or something related with the implementation on that specific version of node.