AGA does not use pavilion angle, but uses pavilion depth percentage because the percentage applies to diamonds of all shapes. The angle varies on fancy shapes, but the percentage depth of the pavilion is the relation of width to depth and is a constant in any shape fancy. The same happens with rounds in that pavilion percentage is a constant where the angles may vary a bit around a stone.
In rounds, the pavilion angle is directly related to the pavilion depth. It is simple trigonometry. The slight variable is culet size, but nearly every modern cut diamond today has virtually no culet facet and is just about pointed. Therefore, pavilion angle is normally in direct relationship to pavilion depth percentage. No need to give people two numbers that generally move in absolute unison with eachother.
As far as BUYING a diamond that you have some objection to, one would be tempted to ask "Why did you buy it if you do not like it?" If you like it, then what is making you annoyed, a percentage number? Don't take it so seriously. You can make excellent judgments about the quality of cutting with percentages and angles, but every diamond is a little different and every buyer hopefully buys what they want. Nothing pleases like the actual appearance of a diamond. It is more than cold numbers and charts. The final analysis of a stone is how well you like it compared to the others you might have selected.
I trust that will answer your questions and raise your spirits, too.