POA for executor of third person's estate

Location: Michigan USA.

I have power of attorney for my father, who is no longer competent. He was executor of my mother's estate. Dad is behind in filing income tax returns; his tax advisers are ready to file his return for tax year 2023, during all of which Mom was still alive. They are asking me to e-sign form 8879 authorizing them to file a joint tax return for my parents.

The tax advisers say, "Since you are acting as attorney-in-fact, you may sign the e-file authorization forms on their behalf. These forms are for our records and authorize us to electronically submit the completed tax return."

Are they right?