Troll alert.
'fly or levitate spell or effect' refers to any spell of that name or effect of that name. Improved Dragon Wings is not the same thing as the Fly spell. It is not based on the Fly spell. It has nothing to do with the Fly spell. Nor, for that matter, the Levitate spell.
To put this more simply. When an ability refers to a 'spell or effect', it's referring to a 'spell or magic effect'. Including but not limited to Spell-Like Abilities; Supernatural Abilities; the Effects of Spells; the Effects of Magic Items.
So, 1. It names two specific spells that you can't use to trigger this feat. This build uses neither of those spells. 2. It specifies spells, not 'any ability that grants flight'. This build uses natural flight, not flight granted by spells.
So, you're not just wrong, you're doublewrong.