2.8" tft screen arduino all pins used
You're confusing the idea of using all the pins to that of plugging into all the pins.

Yes, your shield may well have all the pins on it which then fill all the available holes.  Only some of them will actually be connected to anything on the circuit board though.

The breakout board you link to basically provides a "tee" connection to all the pins, so that you can then get to the pins that, while they may have a lump of metal plugged into them, don't electrically connect to anything at all.

You should look at the schematic for your TFT screen to see exactly which pins are in use and which are there but not wired to anything.