It looks like he got one day a week off on either Sunday, Thursday, or Friday. It still looks like that day was chosen when there was a left-handed starter (please don't waste time researching that because it really is not that important.....).
Luck is probably involved, but his plate appearances could definitely have been closer to 20% against LHP. To his credit he had only modest platoon splits. Clearly Rincones is more likely to be a platoon player than Crawford based on performance and not usage.