Its really hard to say without looking at the HDL or reverse engineering the processor.
Power is determined by switching transistors, there must be more if you using a 32-bit timer. The 32-bit timers (timers 1&2) are complex,they can be setup multiple ways.
There are lots of transistors switching all of the timer while the counter is in use, you increment it by one for certain values and all of the transistors switch of the 32-bit counter. Due to the complexity of the other features of the timer (triggers, pwm, output compare) there are a lot of values and registers that are being compared to the counter value, every time the clock increments some of those transistors switch also. This may be a max power value, and it might be lower if your not using all of the special features.