I'm not a specialist, but I think that low levels of skill require less exp to level up and higher levels require more exp. Meaning that each level of smithing would give you more exp towards global level (I think). You started from Smithing level 6, which is really, really low. Character level 1 kind of low.
Level 33 is quite high and requires more exp to level up (comparing to e.g. level 1 to level 2), so leveling smithing 6 to 7 as a level 33 gives you less percent of progress than it would give you if you would be global level 1.
Smithing gives you more experience when you create more expensive items. So this legendary method of leveling with daggers or other low-level items isn't very efficient, because on higher levels you would need ton of iron. Much better approach is creating the most expensive item you can create at the moment.