Yes, you can forge the URL for now, but it will stop working in March, because we’re deprecating user profile pages (because GDPR means 
).
We’re going to replace user profiles with a content-space for Users or Teams called a Workspace, which will serve as that new reference point, but it will only show what content is contained in that space.
So that is a long winded way of saying that the ability to point people at a user profile via the API is going away.