I agree on quality varying widely for resins softer than something like ABS or PETG. And tolerances are definitely never to advertised spec. It’s worth noting that Formlabs themselves sell a “silicone” resin for a hilarious $350: https://formlabs.com/store/materials/silicone-40a-resin/

At that price point you might as well outsource it or at least print a negative and use a real silicone pour.