Missed this Mike. The OLED on TinyScreen uses SPI for data and commands, but the chip select and other control lines(along with the buttons) are attached to an I2C GPIO chip. This trades 7 I/O on the main controller for an I2C address, which allows TinyScreen to be compatible with all our other boards.
The Wire library has unnecessary overhead, but we want to cause as few software conflicts as possible- you can definitely change the buffers to be very small, 2 bytes should work without causing issues in the library logic, but I haven't tested that.