Because you’re using date_0_startingdate and 0 represents the first row of the repeater.
WP has recently added the ability to query the meta key using “LIKE” https://make.wordpress.org/core/2019/01/23/like-support-for-meta-keys-in-5-1/, but to be honest, I don’t think it will work on repeaters and you’re probably still going to need to use the example from this doc https://www.advancedcustomfields.com/resources/query-posts-custom-fields/ there is a section on repeater sub fields there.
But, then again, I would do this https://acfextras.com/dont-query-repeaters/, but if you’ve already got a lot of data in the site it would mean updating every post. It’s something that you need to plan for ahead of time.
