I guess that makes sense, the oil would have a direct path through the center of the piston so no restrictions at all.
On my loader one of the bucket cylinders was leaking and allowing the bucket to dump by itself in about 20 seconds. Since both cylinders are tee'd, it's not obvious which was leaking. If you dump the bucket all the way, disconnect the retract hose on the right cylinder (or left, up to you), then with the tractor running try dumping slowly. If oil comes out the hose, it's the left cylinder, if it comes out the cylinder port it is the right cylinder that needs rebuilt. Could use a similar method to troubleshoot parallel swing cylinders.
Glad you found the problem!