True fiddleback waist would be expensive to resole.
Faux fiddleback is just like a typical resole job.
IMO, it really depends on preference and the shoe style. Sleek last better pair with sleek sole and waist and design. But for country shoe designs like Hove or country leather like cordovan/pigskin, it's better to have less sleek lasts IMO.
But nothing stops someone to order a cordovan double monk in Deco last and HAF sole.