The contemporary square-drive screw has all but replaced the Robertson screw proper and is commonly referred to as a Robertson because it has practically identical drive dimensions and the same colour identification system, but the contemporary square drive socket has parallel sides rather than tapered.
Which is due to simpler and cheaper machining. Properly tapered Robbies are still available, they’re just expensive as fuck and you have to make sure your bit is tapered as well. It’s 1000x easier to seat a Robertson than a square drive, especially if it’s blind.
Except apparently Robertson isn’t used anymore.
https://en.wikipedia.org/wiki/Robertson_screw
So it is a square drive, not Robertson.
Which is due to simpler and cheaper machining. Properly tapered Robbies are still available, they’re just expensive as fuck and you have to make sure your bit is tapered as well. It’s 1000x easier to seat a Robertson than a square drive, especially if it’s blind.