^^ Yes
Lets forget the pharmacology for a second. Let's view it as simply the unknown dosage factor which is relative to risk. I know there are those who religiously practice safe dosage trials with new batches of G chems. I applaud this attitude, and so perhaps this argument does not apply to them.
But - and neither being a Dr or an expert on drug emergencies - I would suggest that the mean dosage for pills or caps is probably very seldom that which exceeds a "critical" or life threatening dose. Can the same be said of G chems when offered as a single dose?
When an unknown strength tablet has tested positive to MDMA, a user who is conscious of harm reduction can choose to take a small amount, being fairly confident that the dosage will not be too much. Indeed, this is in some ways limited by the amounts of MDMA which can be contained in a portion of a tablet. Therefore the user can - unless his/her test kit has been fooled and the active isn't MDMA - assume with reasonable confidence that a portion dose is less than that which may cause problems.
Quantity can also be measured-estimated in the same manner when talking about a cap or bag of powder. If you measure out 120mg of pure MDMA, then no matter how pure, it is only 120mg MAX.
But G compounds are a completely different story... ...and if MDMA was sold in liquid form, similar concerns would no doubt also exist. If MDMA was sold as a dissolved solid, it would be possible to place roughly the same amount of MDMA in 1ml of H2O, as GHB. Without a doubt, that would be a serious concern.