Compensating for voltage drop across current-sensing resistor in a TL494-based SMPS
I guess they implemented it like this as a way to say "look! you can do current limiting with only one extra resistor!" while it doesn't actually work, as you have noticed (ie, at 10A the voltage drop is substantial). Also it is not protected against short between output and ground.

This schematic is very old! No-one would design a switcher like this anymore. Saturated BJTs are very slow switches, which means the frequency will be very low, and this requires a huge inductor, which is bulky, expensive, and lossy.

If you want to design a supply like this, try a modern chip or just buy a readymade switcher module.