Not necessarily. Again, if that strut bladder inner valve is faulty the strut bladder will deflate when the main bladder is deflated, but will hold the air when the main bladder has pressure.
I assume you don't have any place where to submerge the kite inflated. That's what I do, but I have a pool handy.
If you don't hear a hissing or soapy water bubbles coming out, you can pump the kite and wait.
If only the main bladder deflates, then, oh my, it's the main bladder.
A leaking strut will deflate the main bladder as well, so you will never get only one strut deflated.
If you get one strut plus the main bladder, then aim for that strut.
This will work if all inner valves are ok.
Any faulty inner valve will deflate its strut, even if the strut doesn't really have a leak.