It's definitely true that part of the rationale for installing the AL-31F in the J-10 first was that this engine was a known quantity while the WS-10 wasn't. However, the original plan was a different one, the AL-31F was a short-notice emergency solution and as Hyperwarp says, even in the J-11 the WS-10 initially could not cut it. It's clear that this approach wasn't merely an overabundance of caution, there were known issues of a magnitude that twice forced a departure from the intended path.
As for the rocky start of the F110's career:
Not an auspicious record for an engine that was supposed to help solve reliability issues (it still did, in a way, as such problems now grounded only one engine sub-fleet, but aspirations would have been a lot higher). As often is the case, people's memories are short when touting the reliability of Western hardware.
