Agreed, if the vehicle is a planned, necessary & reasonable purchase, and you can put it on a credit card that you either A) plan to pay in full off immediately or B) have some special 0% or very very low rate promotion, AND it gives you miles/points/cash back to boot, then yes, kudos to you sir/madam for winning.
But the comments on the article were taking on a tone of Kohl's version of "savings" -- which is buying unnecessary stuff to earn rewards to "save". Someone even went so far as to warn people not to fall into the rewards trap of buying extra stuff just for credit card rewards, and was negged out. Spending $200k on a $40k truck every 2 years and getting $2k back in 1% cash rewards is being crafty. Spending 80% less by only buying 1 truck and driving it for 10 years until the wheels fall off instead is being smart.