Fervor of Battle + Life steal/Death's Dance bug

tldr; Fervor of battle functionally works as on-hit physical damage, but items that normally benefit from on-hit effects don't receive benefits from this mastery. IE: Life steal or the new item Death's Dance.

To test that Fervor of Battle was an on-hit effect, I used Poppy's Q and noted that she was dealing physical damage separated from the magic Q damage. I also tested Irelia's Q with and noted that the Q's physical damage was increased with each stack.

I then tested getting a large amount of life steal and noted that the amount of life stolen with 1 or 10 fervor of battle stacks never changed. I then tested getting Death's dance which reads "Dealing Physical damage heals for 12% of the damage dealt." The healing I received with death's dance did not increase as I stacked Fervor of battle.

Since Fervor of battle is functionally on-hit physical damage, I would assume it's a bug that it isn't treated that way when affected by life steal or Death's Dance.

Edit: For clarity, let it be noted that other on-hit physical damage, such as sheen, is affected by life steal.