After the video is created, we can convert it to something more available to the masses. Who cares what he writes it in initially? Let him choose his method, then we will be thankful we have someone talented enough to create it and just convert it after the fact if we dont like flash.
We care because bounties and shares are paid only for free open source stuff, not proprietary stuff. Its the same thing as all the audio files in Linux distributions being .ogg, they apparently have to be because the common alternatives are not free open source codex / codices. (I think we also don't use GIF anymore too, similarly, ever since the big burn the GIFs campaign a decade or so ago or more.)
So sure if his flash authoring tool can also put out a free open source codex or he can convert it as you seem to expect to be possible (googling reveals google themselves made a converter to convert flash to HTML5) then fine, but we don't do bounties or shares for proprietary stuff so any bounty or share would be for the HTML5 or whatever free open source thing not whatever proprietary formats he used internally in his studio to create the free open source end-result.
If he cannot produce free open source but you can by converting his stuff, then it would be you who should get the bounty, and you'd share it out among your team as you see fit, such as to give him most or all of it for creating the flash thing you used to produce the actually rewardable end result.
-MarkM-