His rogatory is his attempt to make sense of his previous statements, without being a witness to anything.
I tend to agree with
@Dlk79
Btu I don't think he even listened, but under pressure early on, he pretended he did do the check so he wouldn't get in any trouble, and to make the group appear responsible.
The most critical thing is he is unwilling to be the last person to see her alive - because he never saw her. But he never expected he would be a critical witness, because he in fact never saw anything.
Had he listened at the window, he would have had to see that it was open. He is also unwilling to say whether the window was open.
But this shows the danger of cross contamination. None of this matters once JT takes Redwood's off ramp. His evidence is no longer under any pressure to confirm what JT and KM claimed. He isn't tempted to think how things "must have been".
This IMO, answers how a smallish act of self preservation in the first confusion might grow into something problematic. By the time he does his rogatory a year later, there is significant legal jeopardy for others if not himself.
Going back to the testimony at Lisbon, I believe PJ has always been right about this aspect of the case - but maybe not for the reasons they suspected.