The "reset state" is what you define it to be. Any state can be used as the reset state provided the reset signal forces the state machine into this state.
It is very common, however, to use '00' as the reset state as it is very natural to assume a counter to be reset to zero.
However, 'zero' doesn't need to be coded by '00'. The assignment of states to numbers is arbitrary and depends on the code scheme used. consider e.g.
Gray coding which is rather different from straight binary coding.
Aside from simply counting, state machines can be used for a lot of different purposes for some of which it may be advantageous to have a reset state other than '00'.
Does it matter if we are considering jk flip flops or some other flip flop?
YOu can answer this question for yourself: design the state machine using D-FFs in one realization, JK-FFs in another realization (not too much work for a 2-bit state machine). Compare the results...