Remember, you can use the 2 shifting paddles simultaneously.
Yeah. You can change both the front and rear derailleurs at the same time. Up to the big ring, and onto a larger cog at the back; down to the small ring, and onto a smaller cog at the back. Up on one, down on the other.
I learned using shifters on the down tube. I couldn’t change them simultaneously. Well, not without crashing. The paddle shifters on the bars are designed so that you can shift easily without taking your hands off the handlebars. When I first began using paddle shifters, I continued to use one at a time, and didn’t realize the benefit of using them both at the same time.
PedalWORKS 
Caveat: For some reason, doing a ‘clap hands’ double shift seems more likely to throw the chain with some groupsets. Changing to the small ring on its own on my bike will never drop the chain, but can happen with a double shift. I’ve pretty much learned the quirks of mine, triggering one slightly before the other seems to do the trick, but I’ve ridden hire bikes etc. where it was almost impossible to manage without coming off the front derailleur. No doubt adjustment, wear, chain tension etc. has an impact here though.
Thankfully, I have never had this problem. I have Dura-Ace and Ultegra groups on my bikes, keep them very clean, well adjusted, and replace the cables every 1-2 years.
Using eTap you need to press both to shift the front mech. You kinda get used to it.
I haven’t invested in eTap (yet) but didn’t know that.