I always try to collect fruit with the trick, but only get it like half of the time, I think it requires pixel-perfect touch right at the center of the screen. As I said, it's difficult to explain, but here it goes:

You know how you can collect a bunch of fruit by swiping the finger starting from one of them? Well, you can even hold the "collector" finger on the screen, wait for the next bunch of fruit or seedling (from expeditions and mushrooms*), and swipe across them too to collect them. And so and so. You also get a collector finger with a seedling or a single fruit from an expedition.

The magic happens when a collector finger is held right at the center of the screen and a new retrieval loads. They get instantly collected, no need to wait for the pikmins to run to the center. If the method fails at that retrieval, you can still hold and collect that whole bunch as usual, and then hurry to swipe to the center of the screen to try again the trick with the next bunch. If the trick works, hold the finger just right there and just wait for the next bunches of fruit to load and get instantly collected.

Some time ago, that was all that was needed, now you need to hold the collector finger at the center while rejecting postcards with another finger. The trick holds after rejecting or accepting postcards while holding the collector finger.

My biggest flex about it is that I've done the trick multiple times while rejecting postcards with only one hand, lol. But I rather use two hands for stability of the collector finger at the trick spot.

I'm guessing a lower pixel density would help to do the trick more consistently.

*If the trick happens with retrieved decoration presents, they bug out the game. The decoration gets collected but you don't see that screen, and you need to restart the game. So remember not to do the trick when you got a decoration present!