From someone not in the hobby: what exactly should I imagine under the term counterfeit batteries? Are those batteries that can be used in the same devices as tge real ones but with different specifications or are they just from different lower quality brands than the one advertised?
They are liable to vent (where they overheat and off-gas dangerously) and/or explode. Stay away from counterfeits like your life depends on it, because it very well may.