All true, but last year Mac was desperately looking for a go-to 3rd down receiver and Meyers was missing. That's what the Pats are looking for.
Bourne has skills other WRs on the team don't have, Parker is this year's experiment at #1, and Thornton is the guy for the future.
It appears they will build Mac's future from there. If those guys above don't work out, the team might commit to Meyers longer term, but if Nixon or another WR shows up in camp, Meyers has to viewed as odd man out, especially looking at 6-8 million after this year.