I believe the NES's 6502 didn't have a logical-OR operator (which is what the situation calls for), only bitwise. The apparent goal was to find out, "Are either

I believe the NES's 6502 didn't have a logical-OR operator (which is what the situation calls for), only bitwise. The apparent goal was to find out, "Are either PLYPS0 or PLYPS1 equal to 0?" They probably started with ORA, and when that didn't work, tried AND, and that seemed to work, so they went with it.