"I was told"

The three most dangerous words.

Since Randy has been around quite a few years, and this is the FIRST time I have ever heard that complaint, I would classify it as pure horse potty.
The other comments above have some value, if you decide to measure the axle. As it's out of the car, it would seem to be the time to do it.

Mark Williams has an interesting page concerning axles. It's worth a read. https://www.markwilliams.com/

The comment that longer splines weaken the axle is a MW selling point. The example is a low cost axle manufacturer that buys blanks with extra length, then puts several inches of splines on the axles, creating a universal part. When you order an axle, the universal axle gets pulled off the shelf and cut to length, most times leaving an inch or two of extra splines. The splined shaft has a smaller effective diameter and the axle would normally twist/fail in that section. If the splines are the right length but just machined where they are needed and nothing more is done to the shaft, the axle tends to twist off at the end of spline engagement. The right way to do it is to taper the shaft diameter down to the minor diameter of the splined area. Then there are no stress concentrators.

I believe that the axle will develop maximum strength when spline engagement equals the shaft diameter.

R.