Student or Learner
Do these words work together correctly?
He says tenable things. (he says wise/sound things)
A statement can't be tenable. A position or belief can.
'Tenable' is from Latin tenere, "to hold". You can hold an idea, a position, a belief, as Bob said. But you can't hold a statement.
However, it's possible that the things 'he' says refer to tenable ideas, plans, or propositions.