Dennis, Not true regarding what your Viper Tech is saying. The tube's purpose is to vent air from the reservoir while keeping the cap from turning. It also assists in stopping fluid "spray" which occurs on the OEM cap because it raises the height excess fluid needs to travel up before making the turn to travel out the tube. This is opposed to the OEM ****** that just allows it to come out the ******.
There is a rubber splash shield on the underside of the OEM cap and small holes at the ****** base that vent air out the center of the ******. Unless you fill your reservoir to the rim with fluid (which isn't following the specs on the dipstick), you will have very little fluid ever make it out the ******, even if you road race. You are overfilling your reservoir if you do. Fill, screw on cap, unscrew, check dipstick for level.
The tube won't siphon fluid from the reservoir because at no time is there a continual stream of fluid between the fluid in reservoir and the downward portion of tube. 2 or 3 inches of airspace from fluid level to top of reservoir, another 2 inches in ******, another couple of inches to arch at top of tube.
His point would be correct if you drilled a hole in the center of your cap, fabricated another vent tube with a longer end, inserted it directly into the fluid in the reservoir.