Toned Tails

While in jail, Tails has to work out regularly and keep his senses sharp just to stay alive. This has the effect of making him considerably stronger and faster when he gets out. At a caloric deficit with low fat intake, his physique would likely become leaner - slimmer and more toned with a mild athletic tinge. At Lily's request, he refines his training further several months before tracking down Sage. Kind of lines up with Frontiers' ending as well now that I think about it. I'm assuming Sonic Team was hinting at something similar during the epilogue, but I guess that remains to be seen.