But it was a direct command from the resurrected Lord to the apostles. An unambiguous one too. (i.e., not subject to interpretation)
So the Lord just couldn't get the apostles to understand him.
No, I'm convinced that Peter was in complete understanding of that command, for the Lord didn't fail to instruct him, or the rest of the apostles.
Peter commanded baptism in the name of Jesus Christ in Acts 2:38; in the name of the Lord, in 10:48. Philip baptized in the name of the Lord Jesus, in 8:12,16. Paul baptized at Ephesus in the name of the Lord Jesus, 19:5
What's to interpret? Do you have children? You no doubt have parents. Are you married? If so, you're a father, a son, and a husband. Is that what you sign on your drivers license, checks, etc.?
The fullness of the Godhead is found bodily in the Lord Jesus Christ (Col. 2:9). Just the mention of his name 'covers all the bases' (3:17).