I guess it's highly likely JMSDF's helicopter dropped explosive sound sources very short distance to 093B.
Unless you have established a protocol of throwing training depth charges --- for example the US and the Soviet Union agreed on three charges --- as a signal for the submarine to surface and make contact with the surface fleet, such actions can be taken as hostile (see Cuban Missile Crisis). The Type 054A would have recorded that, and if you throw those charges outside of territorial waters against a sub, resulting in damage to the submarine, you would be at fault.