DIY plans for Coil Denitrator

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The one thing I seen to be missing is why all the effort either sealing or using fittings where the 1/4" tubing passes into the PVC?

I'm assuming the 1/4" tubing inside the PVC is a continuous loop, the PVC is just to contain the 1/4" in a dark environment and bio-balls are put in, in same plans, just the hold the coil's shape. Wouldn't it work just as well if a couple of holes drilled in the cap a the line passing through?