Is the scum skimming really necessary in pho broth? In nearly every pho recipe that makes claims on "authenticity" there are some steps in bone treatment (some recipes go even further with salt rubs and long cold water soaks etc)


Cover bones in water and boil for 15 minutes.
Scrub and rinse bones under running water to remove all scum (i.e. blood proteins).
Clean pot and add fresh water.
Bring back to boil and meticulously skim scum every 5 minutes during initial hour of cooking.
Skim every 30 minutes thereafter.


That is a lot of work.  I've always had suspicions that pho restaurants aren't doing all of this.  And since that's the bar I'm trying to meat(get it?), is all of this work really necessary?

Also this seems to be throwing away a lot of good flavor in the water along with the scum?

Two points of reference:

https://www.youtube.com/watch?v=FPbwOcE6UCU

This is a restaurant making pho in huge quantities.  They just put meat in bags and call it a day.  In fact the pot is overflowing with meat and veg that they couldn't skim even if they wanted to.

https://www.youtube.com/watch?v=auqu2U5XdsI

This is a no non-sense video that cuts through a lot of known bullshit (MSG avoidance, etc).  Also no scum skimming, and the broth looks clear enough in the end.
It is not necessary in the sense that if you like the finished product then why do the extra work? That said, the scum that you get from boiling bones/meat isn't really the good stuff. The good stuff is soluble flavor compounds that wind up incorporated into the (liquid) broth.

Recipes from test kitchen folks (Cook Illustrated and Serious Eats) usually call for ONE skim. These usually go


Add meat/bones and boil for 15-30 minutes.
Skim.
Add spices and carry on with rest of recipe.


I can't vouch for how pho restaurants do it but in my experience one skim after the initial boil does the trick (and isn't too fussy).