I havent heard this but I use rio lines and like them a lot. They dont seem "abnormal" to me.
I do not like ot overline. I will sometimes go up one but that is it. I think it puts unneeded stress on the rod and after shattering a custom I built i have decided to not overline.
The one line that i did notice a difference with was an Orvis line i was given last year. It was really thin and I hated it, absolutely hated it. Not only did I cast it poorly, it tangled really easily when I stripped it in onto the floor of the boat.
I use both rio and airflo on my single and two handed rods, but they seem pretty equal. On occasion I'll go over one weight, but on my softer/slower action rods, it seems like I'm stressing them. I stick with what the rod makers recommend. On my Loop Spey rods, they recommend smaller weight lines for the rio than what the rod says on the shaft. Almost 1 or 2 weights less, but I think that’s because those rods are designed more for the shooting head systems like Loop adapted lines. Loop lines are actually tailor made for each rod. I think rio is comparable, but airflo is cheaper and easier to cast. I like the windcutter and mid spey lines on my Spey rods though, but that is because the extra mid section comes out and I change up tips and shooting heads like the DC big boy. It all depends on the user and what he likes and what works for him.
"Everyday that you wake up and decide not to go fishing...is one less day you'll go fishing." Forrest Maxwell
I believe that Rio makes the best lines out there. Their versi-tip system is a required piece of equipment in my book.
As for overlining, some rods don't load as quickly unless they have the added weight of a line size larger. (Or at least that was the argument a number of years ago.) However, a fast rod throwing a heavier line will act slow the action of that rod down, and vice versa. I think it becomes more personal choice than anything. I fish mostly Loomis GLX 7 weight rods and match them with 7 weight Rio lines.
I prefer the loops on the Rio's better than the airflow. Rio now includes a type 8, type 6, type 3, intermediate and a floating tip with each versi-tip system. You've definitely got most conditions met with this. I think I just paid $115.00 for the line but have been using them for about 5 years now and love 'em.