That's another thing but 8-pin connectors will always (?) have at least two molex connectors, there are many 6-pin connectors with two molex connectors so it should be enough.
To put is simply, the sata connector was designed as a low-current connector.
The issue is, that connector was engineered with ease of insertion/extraction taking precedence over high reliability of the contacts, that's why there are three contacts per each wire.
By design, it is assumed that some
contacts will connect cleanly and reliably.
I'm discussing deploying the full 2x sata -> 2x molex -> pcie-8-pin suite of connectors.
If the card actually needs 150 W at the connector, you are overloading each sata connector by 21 watts. Doesn't seem that much but if any of those 3 sata contacts fails to connect cleanly the problem escalates very fast. Some sparking, the connector heats up, possibly to the point of melting, the least of your worries is rig downtime.
Same situation for the 1x sata -> 1x molex -> pcie-6-pin combo.
2x sata -> 2x molex -> pcie-6-pin should be reasonably safe as long as you don't exert pressure on those poor sata connectors.
Treat my post as Public Service Announcement, I'm trying to make sure that pitfalls of developing a cavalier attitude to GPU wiring are on everyone's radar
As for the built-in protections only cheap PSUs will take anything along with them at their death.
Still, I why put a rig full of perfectly good 5970 cards at the PSU's mercy?
All hardware will fail, the protection circuit is no exception.