Not exactly. He's talking about percentages of the overall "tax burden" (God, that's a stupid phrase). If taxes were cut across the board, but more for the poor than for the rich (in some as-yet-undefined measure), then the percentage of "tax burden" carried by the rich would increase even if their taxes are actually being cut.

This is the kind of thinking that allows republicans to bullshit people even when they're clearly in the wrong.