Nick thinks that the guys who will be available at OT at 16 would be reaches in the first round. Specifically, he thinks that the top 4 will be gone leaving only Raimann who he thinks has a 2nd round grade. So, if the Saints feel they need a LT, they will need to trade up to get a guy like Cross. So, he is assuming OT will not be the BPA at 16 or 19.
He does think that WR could very well be BPA at 16 and that BPA is the best strategy if you fill holes in free agency. He's just pointing out that if the Saints feel like they have to get a starting LT in this draft, they are really going to have to trade up to get one. But, if they don't add a WR before the draft they are going to have to stay at 16 and 19 to get a 1st round WR.
Basically, he thinks that signing Landry would open up the draft for them and allow them to take BPA at 16 and 19, or move up for LT like Cross depending on if they think they have to get a starting LT.