There were SCOTUS leaks... merely indirect ones
No clerk called the NYT with a hot tip, but there was surely leakage. People telling other people things like, "I can't say what the decision is, but what I can tell you a lot of people will be surprised."
It is a viable theory today that the SCOTUS was initially going to strike down the whole thing and that, quite late in the game, Roberts switched.
When Ginsberg said, off the cuff, that they had to decide difficult questions of severability that was surprising, because severability doesn't come into play unless the mandate is struck down.
If the initial conference vote was to uphold the mandate severability would never have been an issue in any decision.
Anyway... if we consider the theory of a very late switch we also have to look at the shifting Conventional Wisdom.
There was a murmur this week (that I erroneously dismissed, BTW) that perhaps Roberts would surprise everyone. Why Roberts? And where was that speculation a few months ago (when Roberts had probably voted against the IM in conference)?
It is odd that everyone knew the mandate was dead at a time it probably was, in fact, dead, and then a few started to think maybe not at a time when Roberts had probably changed his mind.
It looks like there was a vibe in some circles that maybe Roberts had done something surprising, and maybe a lot of folks would be surprised by the outcome. But not a formal leak, if you see what I mean.