My view is that :

The Boeshield or WD 40 (my old main stay) wouldn't do any harm; and it's a good idea.

The Frigoboat supplied tubing should a an grade of tubing which anticipates the marine environment. As long a it's clear of salt water's direct contact, it should last a number of years. If you bildge is ventilated reasonably and you're not sitting the tubing in any water, it should be okay.

IF you could factory electroplate the tubing properly (like a refrigeration coil's FACTORY applied condenser equipment, for example) then it MIGHT be better. You still have the fittings and bends to deal with.

If you do have spray, then a shield would be a good idea, but I'd still allow for inspection and ventilation.