if your car doesn't work, then theories or at least the,application of them are wrong, if your bjj doesn't work, it doesn't work, the theories or the application of them are wrong.
claiming its based on sound science when it has at best only a,50% success rate is just optimistic in the,extreme, they wouldn't,sell cars that only work half the time
Your entire argument is fundamentally flawed.
A car (as said) is based on sound theories that are proven to work.
If you go out in the morning and it doesn't start, that doesn't mean the theory is wrong or the application is wrong - it means it's broken.
My Land Rover is 46 years old. If it doesn't start tomorrow morning it hasn't suddenly switched theoretical implementation of ideas that it's used successfully for almost half a century - it's broken. The most likely reason for any car to suddenly not start one day would be a flat battery, which is actually the least 'car' part present and most likely down to user error (leaving lights on or similar).
I can only make an assumption about your 50% success rate theory being that in BJJ competition there is one winner and one loser per match, hence 50% success (the winner) and 50% fail (the loser).
So, compare that to car racing - say there are 20 cars competing, there will be one winner. That's actually a 5% success rate and a 95% failure rate.
So no, they don't make cars that only work half the time - they make cars that only 'work' (using the only logical explanation of your comparison) at best 5% of the time.
Then, you could race a Mini against a Maserati. As long as the Mas doesn't break it's going to have a 100% success rate.
Don't get a Mini, they never ever work...
Now race that Mas against a Jeep.
In mud.
Oops, don't get a Maserati, they never ever work.
I'm making this assumption because put a BJJer against a boxer, but only use BJJ rules - that boxer will get wiped out so BJJ will have a 100% success rate.
Now switch rulesets - the boxer will win every time.
So, unless you have some other fantastical notion that lets you dream of 50% I say again - your argument is fundamentally flawed.