Have you opened up a few of these Chinese batteries to verify this, or is this second-hand info?Chinese manufacturers (Alixpress, UPP, etc.) have been known to substitute cells having the same supposed 18650 or 21700 capacity as that of say a legiimate LG 21700 4800mAh cell or a popular Samsung cell. However, the Ah capacity and MCD amp rating is below par compared to a genuine A-grade LG or Samsung cell.
As such sub-par (counterfeit?) cells may not even have a genuine LG or Samsung label wrap. Such cells may have cost the manufacturer no more than $2-3 ea in bulk quantity. They may suffice for casual/moderate ebiking, but not for those interested in sustained performance (power/speed) for one's overall riding enjoyment.
ES has always been known for DIY quality performance builds with sustained endurance for power, speed and cycle life. Thus UPP, AliExpress and other less expensive Chinese ebike batteries are NOT recommended by knowledgeable and experienced battery DIY builders at Endless Sphere (ebikes.com).