I suspect this is mere posturing because it's not up to Congress to mint the $1 trillion coin. It's a decision only the Treasury Secretary can make.
> The concept of striking a trillion-dollar coin that would generate one trillion dollars in seigniorage, which would be off-budget, or numismatic profit, which would be on-budget, and be transferred to the Treasury, is based on the authority granted by Section 31 U.S.C. § 5112 of the United States Code for the Treasury Department to "mint and issue platinum bullion coins" in any denominations the Secretary of the Treasury may choose. Thus, if the Treasury were to mint one-trillion dollar coins, it could deposit such coins at the Federal Reserve's Treasury account instead of issuing new debt.[5][6][7][8]
https://en.wikipedia.org/wiki/Trillion-dollar_coin
AFAIK, Yellen has never made a statement on the trillion dollar coin.
However, the fact that this is playing out against a backdrop of unprecedented deficit spending, government transfers, and Fed interventions means that this time is different.