Emilian here from Okta Support, thank you for contacting us.
If this below is the prompt that the user is receiving, I'm affraid it is not possible to have it changed so it will only prompt for Push MFA. This is an expected behavior as it was built this way so it may offer the user the posibility of manually introducing the code, because in some instances it might take more than 30 seconds (depending on the internet connection) to receive the push notification and it might expire.
Please let me know if you have any other questions or concerns regarding the matter.
Okta Support Team