Jolla Tablet without Sailfish OS vs. Secure Boot vs. OEM

Thanks @zlutor @reviewjolla @plfiorini @bman626 @iliveinpublic @morpog @eLtMosen for tips and support, regarding my Jolla Tablet order from Taobao and my questions at finding whether it can run Sailfish OS alongside it's current Android 4.4.4. I read about Secure Boot ( https://together.jolla.com/question/115096/jolla-tablet-is-the-hardware-locked-down-can-i-replace-uefi/ ) and it made me think, if the devices are manufactured *without* Jolla's consent, shouldn't they be missing the signing keys - this means, installing legit Sailfish OS would *brick* the tablet. But if it does work, doesn't it prove that the Taobao tablets were indeed ordered by Jolla? Or did the manufacturer just manufacture an extra batch, to sell Jolla tablets directly past Jolla?
I'll try to get additional info as I get my hands on a USB keyboard (none can be found in the house right now) and get to see the UEFI setup. If the Secure Boot can be turned off, then I can try installing Sailfish OS and never know if the signing keys are there or not. If it can't be turned off, I'll then have to weigh my options - whether I want to risk bricking the device by trying Sailfish installation, or keep using Android and never know (again) if the device was Jolla-authorized.
Funny though, the seller at Taobao claimed that you could get Sailfish OS installed at 30$ extra payment - they would ship the tablet to Finland for that before delivering it to you. Unfortunately, I noticed this only after I had placed and paid for the tablet. This, however, seriously makes me doubt the claim that Jolla had nothing to do with these tablets.