I would say that it’s valid.
“It’s legal to drive only if e.g. you have a driver’s license.”
It’s not a great way to say things but it is meaningful. The meaning is “only if [unspecified list of things], and [x] is an example of an item in that list”.
> However, the “safe” is only valid if e.g. the used supply lines from the power supply with “native” 12VHPWR connector have a good quality and 16AWG lines or at least the used 12VHPWR to 4x 6+2 pin adapter also offers what it promises.
Here’s my interpretation:
> However, the term “safe” is only valid if certain things are true, e.g., the used supply lines from the power supply with “native” 12VHPWR connector are of good quality…
I can’t interpret the rest of the sentence.