Would you be able to post your routine please? He could be taking short naps because he needs more A time? I haven't tried w2s to extend naps, mine was a habitual short napper until we dropped the catnap but out awake times had to be stretched to 3hrs.
If w2s is working for you, there is no harm in doing it. If your LO knows how to fall asleep, that's great... he probably hasn't yet learnt how to transition between cycles, in which case it is a matter of time and development or he isn't tired enough to want to sleep more, in which case its a matter of adding a little more A