Yes, that's exactly what's happening. Unfortunately it seems there are not only a lot of vendors mislabeling the freebase as the HCl and vice versa, there seems to be quite a lot of confusion as to what exactly it means to be a "salt" or a "freebase".
The freebase is an alkaline compound which is totally insoluble in water, hot or cold, unless an equimolar amount of acid is added. Since it's basically insoluble in water (less than 0.5mg/ml when in 1:1 ethanol/water) you won't measure the pH of the compound; it will appear at 7 all the time because there's very little dissolving in the water.
Freebase is soluble at a few mg/ml in solvents like DMSO, ethanol. Probably THF, dichloromethane, chloroform, dioxane, maybe even ether too. Practically insoluble in water, soluble in acidic water (turns into a salt). You will probably be able to force some amount of AH into solution with very vigorous heating and stirring but what I'm trying to get at here is: don't try to dissolve the freebase in water, if you get it dissolved it won't stay that way for long.
The HCl salt is a slightly acidic compound produced by neutralising the alkaline free base. As knock pointed out, should be almost instantly soluble in water, and should stay that way. The pH of a solution of this should be much more tolerable, too - but it will eventually corrode metals and stuff like any salt would.
Don't store it in a steel spoon overnight.
People reporting problems dissolving the compound in water and "this burns on insufflation", "this tastes corrosive", "can't get it to stay dissolved" etc... you probably have the freebase. For your own good stop putting it on your rather sensitive mucous membranes. (Not that the salts won't burn either - they will be a hell of a lot smoother) And also, don't inject it!!
See, for instance comparisons of amphetamine sulphate (a white, crystalline, water soluble, slightly acid powder) versus amphetamine freebase (a corrosive alkaline water-insoluble organic liquid that stinks like piss).
The usual methods exist for turning one compoud to the other.
Salt --> Freebase.
Dissolve salt in water, add some sodium carbonate (as a solution, preferably) to raise the pH to about 10-11, and then filter off the freebase that's crashed out.
Freebase --> Salt.
Dissolve the freebase in a solvent of choice (probably dichloromethane, chloroform.. somethin polar but aprotic - hexanes, etc won't work very well cuz ah freebase has shit solubility) and add a solution of e.g. citric acid also dissolved in a solvent, or gas with HCl, or add HCl in solution and recover the water layer with your HCl salt dissolved in it and evaporate to dryness.
You can also just boil the shit out of the freebase in a solution of e.g. vinegar, or 1% HCl. Eventually it will all dissolve, then just evaporate the water off.
Oh, the HCl to Freebase conversion rate for AH7921 is 0.90.