I can't find a reference for this, but I believe the guest is given immediate access for 10 minutes, pending approval of their request. This was intended to validate flows where the user's email address is validated - and the user needs an Internet connection to get that email to click on the link to prove they are in control of that email. The other possibility - have you got "Capitve Portal Strength" set to strict? https://documentation.meraki.com/MR/MR_Splash_Page/Enabling_Click-through_splash-page
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