Please see [Link: inscapedata.com].

This lists some differences between using certain CAT5Es, CAT6, and CAT6A... all by the same manufacturer, of course.

In the paragraph after the first chart, it says

This is a straw man. While that seems to sound like it means something, I can't imagine anyone being concerned with the percentage of power that gets to the device, as long as it gets enough to function properly.

Heat dissipation is also mentioned. This could have been an issue in, for instance, a camera system we recently installed with more than 50 PoE cameras. However, the rack is not super-crowded and the room is air conditioned.

Are these things worth paying attention to, that is, using that document as good info, or is it just advertising blather?

Thanks.

it doesn't really pertain to devices running standard 7-12watts Even 20watt POE+ devices wouldn't care at 100M

if you are running 50w+ POE devices, they may have a point.

Wires only care about the wattage on that wire. 50 POE cameras are going to have 50 separate wires.

I have no idea what cameras you used, but the average fixed camera is 7-10 watts.

50x 10 watts means your using 500ish watts.

No, your not going to have any cooling issues.

Incomplete perhaps.

From Belden, certainly a trusted brand:
[Link: belden.com]

Short Summary:
Insertion loss increase with heat due to; higher POE power, bundling, ambient temperature spaces, running near hot stuff. Therefor choosing the right cable is important to reach spec of 100m.

-edit-
Another informative power point link:
[Link: bicsi.org]

Yup- resistance increases with temperature and it doesn't matter why the temperature increases.