Your question sparks a key differentiation between Universal Analytics and GA4. With Universal Analytics, events will record category, label, and value information by default, directly through the actual call itself. For example, the gtag code you provided.

On the other hand, GA4 doesn’t inherently support this. If you want the event_category and event_label in GA4, they need to be defined as custom dimensions and then manually set by you. That’s why it doesn’t automatically work out of the box like with Universal Analytics. Now you know why you’re seeing the descrepancy in event data!