Could explain why you need to plug power directly into your MacBook Pro or MacBook? I use both, and was unaware of this. Any source would be super helpful too.

You may not get the full wattage through a dongle. For example, the Satechi adapter with pass-through charging (recommended by The Wirecutter at https://thewirecutter.com/reviews/best-usb-c-adapters-cables...) is limited to 49W: go to https://smile.amazon.com/dp/B01J4BO0X8/ and search for "Important Notes". 49 watts may be enough for many uses, but (as I discovered recently) not when running a job on all the cores of a 15" MacBook Pro.

Now, presumably the designer of this dongle had some reason to limit the power output. Perhaps the heat dissipation is not enough (the dongle gets pretty hot even when using it just for USB and HDMI). What if some other manufacturer is not so careful and allows negotiating more power through a similar device?

My MBP wants an 87 watt USB-C charger. If you read the product page for the charger, it recommends plugging directly into the MBP's USB-C ports. When I tried charging through the dongle, the battery would charge slowly, or drain a bit when, for example, running gradle builds.