If the decision is that close, it brings into question the exact moment the ball left the other players foot, milliseconds count, that line is on top of the other, football isn’t meant to be perfect and mm lines being drawn by a computer, will eventually kill the game and the spontaneity we all love.
Because the lines and the boots are both blurry - so you cannot be 100% certain. Because from that angle, how can you tell that it was the precise millisecond at which the ball was touched. A millisecond earlier, and the 'blur' would be different.
I despair sometimes. I can only understand this viewpoint from armchair fans - no, I take that back, I don't understand it.
I wasn't really looking for a genuine answer. It was more a rhetorical point aimed at people who seem to think the problem with VAR offside decisions is what part of the body they use to judge it. I don't claim to know what the answer is, but it isn't using feet (as this shows), it won't be "any part of the body onside", it won't be "daylight!"
There is a fundamental underlying disagreement - the authorities absolutely trust the accuracy of the technology, and believe that offside is offside. Others don't trust it, and believe there should be some wiggle room/margin of error. And changing those sorts of idealogies will be tough, whichever side budges. The only simple solution is to do away with offsides. Anything else will not be as simple/successful as some people like think.