I can totally understand the different opinions, but overall I think the possibility to also customize another truck is quite nice.
It definitely leads to a bit more diversity on the roads again, although, of course, it's not something for everyone, but I think a DLC is not capable to make someone like a truck they had disliked before.
Definitely it would be cool if the DLC was also available for multiple trucks, but I guess rather something than nothing, even if it would be better with more vehicles for sure.