It's certainly doesn't generate much trust to have Kremlin involved in any way in anything. However, Jolla's licensing practice AFAIK gives the licensee full access to the source code of Sailfish OS. In that regard hiding some backdoor in the product would be more or less stupid idea in the first place. However, because manufacturer can add their own stuff, it boils down to question whenever do you trust either Jolla or the device manufacturer.