So I did find a page that mentioned this on this site but it's wrongly titled Phillips screws.
I just learnt this recently and after 45 years of pulling apart Japanese motorcycles (and cars), I wish I'd known about JIS decades ago.
The screws on Japanese bikes (and cars) that look like Phillips screws are actually Japanese Industrial Standards (JIS) and are very square in shape where Phillips screwdrivers have an angle at the end and are designed to 'cam out' at higher torques. Many times they will have a dot on the top that tells you they are a JIS.
This is why when you try to remove the screws on a float bowl for example, you butcher the screws. As soon as this happened to me, I used an impact instead which sort of fixed the problem.
Now I've found out it's because Phillips screws were designed for Aeroplane construction to 'cam out' before they stripped the screws in the aluminium. Jis screwdrivers work well in both Phillips and JIS but Phillips are only designed for Phillips screws, not JIS.
This is a picture of showing the differences:
Don't confuse either with Posidrive. posidrive are similar enough to Philips but if you try to use a Philips set you will likely strip your screws as they don't fit properly.
The angles of the flanges are different. You can identify Pozidriv by the cross on the screw. The bits themselves will have an extra set of flanges, as you can see in the image above.
I bit the bullet and bought a nice set of screwdrivers for $63 plus post from Rhino Tools in Sydney, Australia. You can buy cheaper JIS screwdrivers on Amazon, but two of the four I bought are unique in that they are also impact screwdrivers. They look like normal screwdrivers and have a nice soft handle but they have a steel cap on the end and if you give them a tap, they rotate counterclockwise 12 degrees.