Those twisted things aren't for support. They are called turbulators.I had to know why so I took the plastic tank off the removed heater core. There are plastic twisted support things in all the tubes! No doubt to keep the tubes from getting squished while being assembled. BUT, seems like they should have removed them before putting the tank on. These essentially blocked 80% of the flow. No wonder it didn't produce heat.
Had the old leaky factory core and removed the tank, sure enough, no plastic things. Going to see if I can get a picture posted.
They don't need them because it's built like a little radiator. The tubes are thin and flat seems like creating a lot more surface area. The Brass Works was $360 and 3 month wait, but worth it.I'll bet Brass Works uses them too although they may be made out if metal.