uphill sprints…LOL
What nonsense is this!?! No one willingly sprints uphill. 
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On the flats, raw watts matter more than w/kg. So a heavier rider will see and advantage.
On the descent, with the assist of gravity the heavier rider will go down faster assuming they are the same height,
On the climb it somewhat evens out since it is more dependent on w/kg, but when you factor the bike weight, which would be a bigger percentage of the total weight for a light rider vs heavy, the heavy rider at the same w/kg will go faster.
Light riders at the same w/kg will lose in all aspect, but if they stay under the wattage floor, they are allow to produce over the cat limit and still ride in it.
People keep saying this but it’s not really true. Heavier riders have a much bigger Cd.A than lighter riders do in Zwift. If they are also taller than the lighter riders (which is probably the case on average, though not always), then that also increases their Cd.A still further.
It would therefore be more accurate to say that heavier riders only have a moderate advantage on the flat (in terms of speed vs W/kg), but that’s still enough to skew the game in their favour when there are hard W/kg thresholds.
Heavier (and taller) riders definitely have to produce a lot more raw watts to match the speed of lighter riders on the flat. I used to TTT with some small light guys and when one of them was at the front I could be doing more watts than them just to hold their wheel…
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And rolling resistance that is directly related to weight.
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Heavier riders doesn’t, taller rider does. But they are usually closely related. But there are outliers of short stocky riders that this doesn’t apply.
u get out the saddle at all whilst “sprinting”…?
they were doing literally double ur power lul
time to start lifting 
doesn’t what?
Heavier riders definitely do have increased CdA. The approximation they use assumes that frontal area increases with weight.
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You do if it’s needed.
All sprint finishes should be at the top of a 20-25km climb at 6% average. 
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Had some great races on zwift but had more non races with users who zwift will not sanction or even engage with them and make them aware 300 watts is not normal
Heavier riders don’t have a higher CDA, but taller one does.
That is not accurate.
Cda = Cd x a
Cd coefficient of aerodynamic drag
a aria= length x width
Width derived from weight.
What you are implying is real life, but not Zwift algorithm.
And mass does not equal volume (frontal area). Depending on your muscle density you can have the same weight and height in real life and lower drag, because everything is compacted.
Do you have proof?
Zwift need to make some assumptions, see the formula on how to make some assumptions using mass and height.
Do you have sauce, can make a simple test. Do a bot ride as your baseline. Then add 10cm and you will notice the sauce draft will increase because of an increase in drag. Now go back to normal and add 20kg and test at the same speed. You will notice there is no changes to your sauce number vs baseline.
I don’t have sause so you are welcome to do the test.
I just did the test and you are right, dropping 40kg my draft benefit dropped a lot given the lowe CDA.
I am getting the assumption benefits, my avatar is really yoked. Probably 5-7% body fat vs my 20%+
This is incorrect, it’s easy to show that CdA varies with weight in zwift, as I and others have done years ago.
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