By law the engine must work and out put the amount of power it clains to.
By law the importers must be able to supply parts for a specified amount of time post sale.
The support period varies depending upon the juristricion.
Support costs a lot of money.
Quality control costs a lot of money
Nearly all of the cheap batched engines from China have neither and the importer simply holds a few engines back to cover warrantee replacement then it is tough luck if it fails in 3 years time.
You may get an excellent one that will give you 20 years of faithful service, You may also win the lottery, how lucky do you feel ?