Why is it not recommended that a lambswool roller not be used to apply decking oil. This method should get better coverage as the deck we are going to apply it to is outside and even after sanding will not be fully flat.
No idea. As far as we can see many of the big brands in decking oil also produce lambswool applicators and recommend them for the application of oils. Where did you read that these were inappropriate?
Here's an article with some general advice on applying decking oils and applicators.
The BUILD team.