Why didn’t Emma mention the alleged “You should have played along.” comment to Lee?

Because she's hopeless.

I don't think there was time to go through every lie he told!

Yes, that'd take 2 weeks of rolling VTs!

Too little time, too much to ask.

Because it would not be fair on Casey to repeat the lie.
Bad enough that Lionel kept repeating it......even though he knows it's a lie, he still keeps repeating it....and then saying but it was a lie.

Because he didn't stop pushing his BS for the entire interview. He would have only lied anyway