I assume the engine was not running when you blew into the vent hose. Since there is no manifold vacuum to close the diaphragm, the air you blew into the vent hose went into the intake manifold.
If you were to remove and plug the hoses that connect the CCV to the manifold, you might be able to blow enough air into the vent hose to create the bubbling.
If your purpose is to identify a clogged dipstick guide tube, it would be easier and more direct to remove the CCV drain tube, connect a hose to the dipstick tube and blow through that hose.
2001 530i/5 S+P CDV delete/Akebono ceramic pads
M5 SSK/RedLine MTL/M5 rear sway bar/Bilstein HD
BMWCCA Member #337964