I think Lampards reasoning is fair.
Long season with a lot of games, eventually the likelihood is that some of these squad players will need to play.
Add to that that a lot of them players, as he said, are players with a lot of experience and appearances. They should be able to, and need to be able to be called upon if needed for the first team.
He has also used this to prove a point that the squad just ain't good enough and the shitheads from last season need turfing.
That team on paper is good enough to beat Bournemouths reserves. Thankfully we won't be seeing Michael Keane anytime again soon.