Yes, buying batteries online can be risky. I have noted after a disassembly of an online battery that the sellers tend to misrepresent the actual capacity of the batteries. I am not the only one who has noted this in their postings. The other day we had a guy who bought some batteries "rated" at 80 amp hour of capacity, they were less than 25 Amp Hour of capacity. (I suspect they were less than 10 Amp Hour). A 30 Amp Hour pack I bought, ended up being 20 Amp Hour of capacity.
It is definitely the "wild wild west" when it comes to battery resellers online. Some brands have become well-known for poor construction, or exaggerated specifications (like UPP), and have become banned for use in places like the UK and New York City.