I took a look, and there's a hidden "spin tunnel" tag object there (they typically are used to propel Sonic into a ball a the ends of a tunnel)! It is used to force Sonic into a ball when hitting the spring. This tag object is also quite sensitive, which is why you can get propelled even if you are just *near* the spring. Interestingly, the 2011 remake lacks this object, so the described effects do not occur there.
I think a big reason that TubeSwitch (CD11 script terminology; so cool to learn the CD93 terminology above!) object exists is also because of the Spring Cage just to the right of that area. When it shoots you to the left you go zooming back towards the double loop instead of in CD11, where you just stop dead in your tracks on top of the Red Spring. I've recreated this object in Sonic CD Restored a few weeks back and people can experience it in the current download.
