Even the mouth-breather rookie the dealer service manager assigned to install oil filters could probably manage to bolt the filter housing to the intake manifold and attach a couple of flex lines without making any catastrophic mistakes. Bending and flaring hard lines and getting them routed correctly took a bit more skill and time to do. It was mostly economic concerns, not "better" practice to use flex lines. That also allowed for some leeway as to the position of the filter on the manifold runners- - - -ahead of or behind the carburetor, etc. I've even seen some large-canister filters mounted on the inner fender well or the firewall with longer flex lines on bigger rigs.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!