MAy I add another thought that is from left field. The referee showed the GK the yellow card twice! Remembering referees have previously been sanctioned for this.
Please discuss........
Watched again - I think he’s reached for the card straight away, then used that same hand to call the GK over (so you see a flash of card). You’re right though, others have been punished before, although never understand why the authorities get so concerned over such things, unless it actually causes confusion on the day.
The YC reason is interesting, as people have said. I feel it’s one of those that (probably wrongly) you have to give a YC if not a red, in order to ‘sell’ the decision.
On the whole game system, you can’t actually log a YC as stopping a promising attack (even though it’s in the laws) but ironically you can just put HB for handball!