Firstly, the configuration you want to do does not exist, the splash page will ask for another credential and password and not the PSK. and yes if you are using Click-through it is expected behavior (Users must view and acknowledge your splash page before being allowed on the network).
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.