Google (Or Apple) is pretty serious regarding their app stores rules and regulations.
Google owns the app store. So, developers should abide rules imposed by Google although the rules do not seem reasonable all the time.
My suggestion is, developer can still implement in-app billing, removing "donation" wording. For the in-app item, make it as good-to-have feature like "unlocking additional app color theme".
With such, he will still abide the rule, yet able to get his monetary reward.
Google owns the app store. So, developers should abide rules imposed by Google although the rules do not seem reasonable all the time.
My suggestion is, developer can still implement in-app billing, removing "donation" wording. For the in-app item, make it as good-to-have feature like "unlocking additional app color theme".
With such, he will still abide the rule, yet able to get his monetary reward.