Correct, Molex to SATA adapter/splitter cable omits the 3.3v line by default and would alleviate this issue. I tend though to be bit reluctant to recommend those to folks that are less experienced with these sorts of adapters and general internal workings of computers (no disrespect intended)due to the legitimate risk of melting and/or fire that some of the Molex to SATA adapters carry.
To be specific, there are two types of female SATA power connectors you tend to see - ones where the plastic is a matte finish and injection-molded around the wires; and ones similar to what are on that cable in the STH forum post you linked, where it is a shiny finish and the wires are crimped/punched down/staked into the connector and it pierces the wire insulation to make the connection. The latter, where the wires are crimped/punched down, and you can open the back of the connector and unseat the wire from the connector, are generally considered "safe" to use (I've had MULTIPLE of this style deployed in my NASes for years without a single issue. And indeed I pulled the 3.3v wire out of the back of them to solve this issue for myself).
The ones that look all nice and pretty with the wires going into the back and the connector is nicely molded around the wires are generally considered NOT SAFE and carry a risk of melting and eventually fire. And it's ABS plastic, which is happy to provide itself as fuel for the fire
Not safe example (SATA ends are all nice and pretty looking, the connector's injection molding is done directly around the wire insulation (which is bad!!!)):
View attachment 539635
Another
not safe example (the female ends downstream are the safe kind, however the male end at the beginning of the chain is the
molded kind of connector, which is
not safe):
View attachment 539632
"Safe" example (you can see the back of each connector, including the male end at the beginning, has a clip that pops off that helps to hold the wire in place where it is punched down/staked into the back):
View attachment 539633
Note, this ^^^ one is a SATA to SATA splitter, and would need the 3.3v line removed or cut from this splitter in order to fix the problem.
A "Safe" Molex -> SATA splitter (no 3.3v issue) (the SATA ends again have that cover on the back to help secure the wire as it is staked into the connector, meanwhile the Molex end... Molex is about as simple as it gets. It's a shitty connector IMO but hard to go wrong there, really (the Molex end is safe)):
View attachment 539634
Another "safe" variety of Molex -> SATA splitter (no 3.3v issue, this is a different kind of SATA connector where even though the wires go straight into the back of the connector (something which is bad on the other ones), you can see how these connectors have little tongues to hold the individual pins in the connector in place, and those pins are physically crimped onto the wire. The connector body is NOT injection molded around the wire insulation in this case):
View attachment 539636
Of course there are caveats abound - I say "safe" in quotes because every one of these connections you add increases resistance along the circuit at the connector junctions, as well as each disk you add increases the current draw and the main cable that comes from the PSU that you are connecting this splitter/adapter to may not be rated to support that much current, then it overheats and melts or burns.
For someone just adding 2-3 extra disks in their system, realistically it's pretty unlikely it'd ever be an issue. For someone like me who has in some cases 2 of these 3- or 4-way splitters on a single 3-port SATA cable from my PSU in order to power 8 HDDs on one cable... maybe pushing my luck a little, maybe probably still kind of sort of OK. Don't be like me.
(PS... sorry for the novel!)
Also, just to mention - for context, the one in the STH pic is a PSU SATA cable, and that has the "safe" crimped/staked connectors on it. I don't believe I have EVER seen a PSU SATA cable/connector that is the unsafe injection molded kind. Case in point, the connectors Nocto posted in their pic are all the safe variety.
