I'm going to take a stab at this, even though I've only played a little of the game. 71 and 29 add up to 100. In the military/social/science sliders, each represents a percentage of total output. So with the figures provided above, I'll assume the science was set at 29%, while social and military added up to 71%. That is at 100% spending. The fact production and science are in different unit measurements doesn't mean both are at their max amount with 100% spending. The percentage of their total is determined by the mil/soc/sci percentages. When the mil was set to 100%, naturally mil should be 56 and the others 0. Since your production max is 56. Same if soc were at 100% and the others were at 0. Since science is in a different unit, and your science max is 24, with spending at 100% and using 100% sci, the most you will get is 24. Since it's all going to science, the social and mil will have to be 0. The mil/soc and sci use different figures and the percentage of total production is subtracted from these separate figures. Mil/soc percentages are only of the 56 figure, while science percentages are only of the 24 figure. If you were doing 1/3 mil, 1/3 soc & 1/3 sci at 100% spending, you should have 18.7 (1/3 of 56) mil, 18.7 (1/3 of 56) soc and 8 (1/3 of 24) sci.

You cant have both 56 mil/soc and 24 sci at the same time, unless you could figure out a way to have 100% science at the same time you have mil/social adding up to 100%.

FWIW, you're far from alone in this sentiment.

It's possible to be somewhat more efficient by using the "Focus" feature, which allows you to convert a quarter of a planet's research output to production or vice-versa.  Click on the little button next to the relevant number on the planet screen, or on the number in the civilization manager.  This is the basis for the "all labs" or "all factories" strategies that you can find if you read around.  Essentially, either keep your research level at 100%, build no factories, and divert focus to social/military production when needed, or you keep your research level at 0%, build no labs, and divert focus to research as needed.

How your scientists construct buildings, or your construction workers produce scientific breakthroughs is left deliberately vague, but it does allow you to run your economy at full capacity.  I usually run all-labs, and try to keep enough of a budget surplus to fast-buy the production items I need.

I'm pretty sure the answer is no.  For one thing, changing a basic mechanic like this would require the AIs to be rewritten.