Why are Windows semiannual updates named H1 and H2? (devblogs.microsoft.com)

I knew it was "Half 1" and "Half 2", but didn't know the rest.

And now that the season bias is pointed out it seems obvious, but I never thought about it before.

I moved from the UK to Australia 25 years ago and took citizenship 10 years later.

However my brain still thinks of spring as being March or April...