Every Google Wallet pass class carries a review status. A class starts in draft while the design is being worked on, is submitted as under review when the issuer is ready, and Google marks it approved or rejected after checking it against its policies. Passes can be saved against a class once it has been submitted, so review does not block a launch from being prepared, and the status applies per class rather than per pass.
The review is Google's check that the pass is what it says it is: that a loyalty program is a loyalty program, that the branding belongs to the issuer, that the content follows Google Wallet's acceptable use rules. It is lighter than the Apple VAS entitlement review, which concerns NFC access, and a rejection usually comes with a reason that a small change resolves.
Review status sits alongside a second gate on the issuer account. A new issuer account runs in demo mode, where every pass shows a test-only banner in the wallet; production access is requested once, after which the banner disappears for all the account's passes. Both gates need to be through before members see a clean pass: the issuer account out of demo mode, and each class approved. A platform that has been through both many times will know how long each takes and what Google looks for.
Apple has no equivalent. An Apple Wallet pass is accepted on the strength of its signature; the only Apple review a loyalty program meets is the VAS entitlement for NFC, which Stell prepares as a VAS Provider.