Bitrise seem to deal with a niche market (mobile development), so claiming their study shows a general trend in the self hosted git market is a stretch at best. I'd imagine boring old git itself and non-website backed things like gitosis are still a massive part of the overall install base. In any case, the claim that gitlab's on 2/3 market share just screams disingenuous marketing fluff to me and cheapens gitlab as a whole.