Although pill weight wont tell you how much active CNS component is in it or what is in it.
Certain things like pill diameter, weight, colour, etc can be useful in assisting to identify certain batch runs. Its not set in stone but the more info supplied the more armory you have for id purposes.
I certainly would not write off pill mass as useless information but information than needs to be fully understood to grasp anything useful from it.
I find Edata and Pillreports although sometimes useful also need to be treated with a certain amount of caution. ie questions should be raised about the source of the information, the accuracy of the data and also in many cases the fact these sites are USA based so are often restricted by the DEA clowns trying to control how we should breath and walk.
Edata for example will only tell you MDMA ratios (due to DEA restrictions) not the actual Mg quantity. Even if you are told the mg quantity there are other factors that can make this figure varied also. For example what salt is the MDMA is the MG the MDMA molecular mass or the MDMA salt molecular mass? in many cases it doesnt really matter ie its either a strong pill or a weak pill BUT my point is all this information is a knowledge tool not something you draw specific conclusions by just cause a random raver has uploded a pic of a yellow pill and said take this and you will ROLL ballZ.