If it's use is id'd "interior" specific it, most likely, has no UV protection. UV protection is found almost exclusively in varnishes intended for exterior usage.
Respectfully rvreclus

When you open the rode tube spar varnish smells the best.

Hello
U.V. protection is paramount especially when it comes to fiberglass rods.

As someone whom has done extensive testing, coupled with a lifetime at the bench where countless fishing rods have been brought in for repairs, other than accidental breakage.The detrimental effects on fishing rods being exposed to Ultra Violet Light and Heat has been the most common distructive issue.

If your making fishing rods that are only going to see the light of day 10 days a year don't give it another thought.If not take the necessary steps to prevent or at least retard the effects of U.V. exposure.

Only a fool would disregard the harmful effects of the Suns Rays or possibly someone to lazy or cheap to spend the time and take the steps needed to protect the rods. My Opinion Yours May Differ.

Tight Lines And SPF 30 Loops
Andy M

Glassmaster will have any contradictory technical detail, but I don't think any waterbased finished has the proven durability and lasting protection of spar varnish. I'm sure such finishes work well but I don't think their long-term trial can be complete. For the hobbyist, tried and true, if it ain't broke don't fix it, dance with the one that brung ya', an ounce of prevention . . . and so on.

Very doubtful--unless there was some flaw in application--there is anything problematic in your rod as described. Spar doesn't necessarily "feel" hard. The harder the finish, the more brittle and prone to clouding and checking. A varnish finish is flexible and resilient. If it doesn't gouge or scar easily with a fingernail, it's probably fine. If it does, it was probably applied too thick and could be stripped and done again. On the blank itself, you have a hard job to put it on too thin, a wipe or fingertip rub being sufficient to provide its protective qualities.

By all means, experiment with the water-based on another rod. It will probably look great and last for years. For now, stick with the product you chose; it is not going to fail and you will have the UV protection. Without arguing its necessity, I'll just generalize to say that all things weather, and spar varnish has protected against the harshest weather possible for decades. viewtopic.php?p=230370#p230370

Polycrilic has been a good color preserver for me on some threads, is easy to use, and does provide a good base or leveling coat. I have always coated any polycrilic wraps with spar and feel they look best when so coated. If you have stripped a blank--vintage or otherwise--apply some spar to the blank for UV protection. Turkey basters work well.