That tells the user nothing useful. Is it 3 oz of Iron or 3 oz of lithium. You give up everything useful about a substance for it weight. That is like basing your health on weight. Dr. note patient is 184 lbs. That is all the doctor wants to know. Yep it is a healthy 184 lbs human. Useless.
Now those genisus have used a mirror trick to say it still is mass but it is only measured in eV. That is electron voltage people. That is saying it weighs 30 volts. Bananas. These people get trillions of dollars measured in volts to prove its voltage. Read any paper in the last 5 years and every mass reference is in eV.
So what is it weight or voltage. It can't be both of them cause mass is 1 dimensional. But then there are the real nutjobs who point to an object point and say it massless. That means no point. What is the point of that.
When you can corner one of these physicists and ask them these simple questions their response is "We do this to keep it simple", or "Ask Newton". He is dead. Ne is not the point. If you are a physicist and you want to KISS "Keep It Simple Stupid" then go into plumbing or ditch digging. They make more money than you and they make sense when they talk.
When you dismiss all the variables of an object for just one you loose the point of physics. Electricity uses 3 variables. Magnetism inverts those three variables. Photons use the variables to transmit heat. Phonon use 3 variables to oscillate density. Magnons use 3 variables to oscillate longitudinal magnetic waves. And gluons use all the variables to determine density.
That is why mass should never be used in physics. It needs to be dismissed like the flat earth, or the earthcentric universe. It is pointless to discuss an element by its weight. That is nonsensical.