Emulator

I played through the game just recently and I didn't see any issues. It played like a normal RPG. Can you provide video saying that it's wrong?

I'm unfortunately not set up to provide videos using real hardware which would show the comparison. The problem is simple though, the player character moves roughly 3 times faster than he should while the rest of the game moves at the expected speed. For those who have played this game extensively on real hardware (gamecube and ps3) this is really noticeable and ruins the immersion.

I've just checked, it moves about the same as on console. I have both here right now, one on my capture card. Is there something I'm missing?

I'm not sure, I found some videos online that show it. Maybe its present only on some platforms?

Real hardware (Skip about 9 minutes in) and this is the expected speed.
https://youtube.com/watch?v=u70c62CA6wY

And a video taken using Dolphin, just watch Lloyd zoom around...
https://youtube.com/watch?v=7kUblwtzmoI

Very noticeable when you walk diagonally on real GCN controller (adapter for Wii U) then on keyboard.

Yea, this seems to be related to controllers. I plugged in my PS3 usb controller I don''t normally use and found it was not nearly so bad as my Gamestop Xbox 360 controller.

Both controllers have been added to the retroarch-joypad-autoconfig github repo if more information on them is needed.

https://github.com/libretro/retroarch-joypad-autoconfig/blob/master/udev/Logic3%20Controller.cfg
https://github.com/libretro/retroarch-joypad-autoconfig/blob/master/udev/Sony-PlayStation3-DualShock3-Controller-USB.cfg

the "problem" of character's movement speed is related to the use of the capacity EX personal of Lloyd via a gem EX lvl 2.

http://i.imgur.com/1syyb6S.png?1 (french version)

I considered that too, but, the save file they showed was too early in the game for them to have that.

Its certainly not because of the capacity EX personal gem. Its because of the xbox360 and sony ps3 controller design which is apparently different from the gamecube controller. I received a raphnet GC/N64 to USB controller in the mail today. The problem entirely vanishes when using it and a standard nintendo gamecube controller.

http://www.raphnet-tech.com/products/gc_n64_usb_adapters/index.php

I'm not sure there is anything that can be done to compensate for this with other controllers although it would be nice since many will obviously be using them, but for me this issue has been worked around.

As has already been discussed, that is not a solution. Unless the radius can only be changed for the diagonal axis and not for left/right and up/down.