Question - Why (on the leftmost type of breakout board in the readme image) is SCL and SDA used for SPI?

[kaptsanovb]

Aren't SCL, SDA I2C pins? Why aren't SCx and SDx used specifcally on that board? I looked at this datasheet, and on the 4-pin SPI connection it shows:

(Acc -> Board) SDO (Im guessing SAO on my board) -> MISO SDX -> MOSI SCX -> SCK CSB (CS) -> CSB (CS)

I did try to connect it through SCX and SDX, but that didn't work.