Back then, certain times (early June, big government meetings) would see a crackdown on VPNs where, so far as I could tell, they just threw down crude blanket blocks on anything they sorta-kinda knew was a VPN but couldn't procedurally target-block. It would (usually) still connect but be rate-limited to essentially nothingness.
I always got the vibe that they sort of informally tolerated VPNs above a certain threshold of sophistication, figuring that they were more interested in blocking the low-hanging fruit that the unwashed masses could easily use, rather than something more sophisticated that only a few techno-nerds could utilise. As other posters have said, they'd know who was doing it and preferred to come knocking with a rubber hose if those people caused too much in the way of issues.