Titleist puts a great deal of effort into providing consistency from ball to ball, lot to lot. I don't know if the different lines vary in weight, but most of the variance from one to another can be best explained by the number of layers, core compression, and cover material. What is important the USGA doesn't specify how tight the tolerances need to be. A 1.48 and a 1.61 weight both meet the specification but if both were in the same box, that would affect your expected outcome. Would a retailer with a contract supplier control the tolerances?

I know this sounds crazy, (but I am kind of anal) I weigh any good Titleist golf ball I find on the course to make sure it is the correct weight and not water logged. They are all 46 grams. I might find one 45 grams from time to time, or even 47 grams. Anything over 47 grams and I won't play it.

Typically I will only put the most recent version of the Pro V or NXT Tour into play if I happen to find one in excellent/mint condition.

I keep all other Titleists I find and don't plan to play in a large bin in my garage. I use them on my backyard range along with other brand balls I find in great condition. I also sell other brands on Ebay when I have a dozen mint ones of the same model. I have thousands of great used balls I won't ever use on the course. 98 percent of them weigh the exact same amount. So, even if the lower limit for conforming golf balls is not specifically stated by the USGA, I would bet there is no benefit to a lighter ball, otherwise I am sure I would find some in my thousands of balls, which weigh in lighter than others. But that is not the case from all those I have tested.

I had open one box of brand new Pro V1, Here is the data measured on each ball of weight variation:
Mark66 - 45.62, 54.66, 45.69g
Mark77 - 45.54, 45.74, 45.68g
Mark88 - 45.72, 45.61, 45.60g
Mark99 - 45.68, 45.65, 45.71g

The variations are between 45.5445.74g= 45.64+/- 0.1g, quality consistency is +/-0.22%. But it is still lighter than USGA rule maximum of 45.93g, the comparison is 0.29g short. 0.63% deviation

I suspected that maybe gravity difference between two different location on earth when measured.

I gave A+ score to Pro V1 ball.