Why do the SSH formats vary between Repo creation and after creation? (BB-9993)

When you create a repo you're advised to push what you have to a repo like:

ssh://git@bitbucket.org/b9chris/brass9sln.git

But once you've done so and access the repo as you will from then on, the SSH url format changes to one like:

git@bitbucket.org:b9chris/brass9sln.git

I've noticed TortoiseGit fails with the first format, but works fine with the second. Why use 2 different URL formats depending on what stage of life the repo is in? Seems simpler to canonicalize to just the main format (the second one).