I disagree. Scotty Cameron thinks that near 4° is the correct loft for putters. A number of his new putters are made to 3.5° of loft. If Scotty really thought that 2° was optimal, he would make his putters with 2°, not 3.5°. I think your fitter was mistaken.

Because people are different and have different strokes. Depending how you putt will change the angle of attack on the ball. Yes, some people compensate by having their hands pressed forward. Others do not. Place the placement of the ball is different for people. That is why best to get fitted for your putter and your other clubs.

I don't believe those two numbers are always mutually exclusive. I believe he is saying your angle of attack should be 2 degrees which is hitting just up with your putting stroke. The 4 degrees of loft will be affected by your angle of attack for sure if you have a completely stable and straight hands to face and hit the 2 degrees up you could have an effective loft of 6 degrees. I always control this by adding shaft lean before and through my putting stroke. Of course the standard loft can be manipulated a lot of different ways both increasing and decreasing to affect loft but still get a +2 degree angle of attack.

First, 3.5 degrees is the stock loft on all scotty cameron putters which is a blend of what most tour pros use. Second, for a 2 degree putter loft you are essentially almost going flat...you need some loft to get the putter up and off the turf initially. the position of your hands also can affect your optimal loft. For instance, one tour pro delofts the putter so much he needs 6 degrees of loft, he has won the masters also...so he is a solid putter...that doesnt mean it is right for everyone. Just some random thoughts...

It also depends on the greens you play. I believe most golf courses keep their greens slightly longer than tour conditions. The putter would need more loft to lift the ball out of the depression to get it rolling.