Is it necessary to condition if kegging in Cornelius with CO2?

Don't add sugar, don't bottle, don't cellar.

Once fermentation and fining is complete, keg it.

Force carbonation is next.

There's a lot of methods you can do to shorten time etc. I recommend this for your first time; put keg in cooler, attach 15 psi. In about 5 days the beer is ready.

Answer: No, there is no benifiet to leaving a kegged beer for any length of time at room temperature. Warmer beer actually doesn't absorb cO2 as well as cold beer.

Some do practice natural carbonation in the keg. Then you treat the keg just as you would a bottle for conditioning. Then attach to co2 for serving.

As far as I understand the description "and condition at room temperature for at least a week" it is for the yeast to eat the sugar to carbonate the beer. That is called "bottle conditioning".

As "Beer & Brewing Magazine" says:

Bottle conditioning, when done properly, can result in a beer with a finer, silkier texture of carbonation, superior foam retention, more complex flavors, longer shelf life, and better aging ability than beers that are “force carbonated.”

https://beerandbrewing.com/dictionary/iKSxvCoDdk/bottle-conditioning/

You can do the same in kegs, in Beersmith there are two carbonisation methods "keg with priming agent": table sugar and corn sugar.