Still doesn’t read as a resignation...hmmm
It does have an ambiguity about it, both Trump’s tweets and Barr’s letter.
Seems like part of the plan, keep the enemy confused.
I think he was fired but allowed to leave gracefully as long as he complimented Trump in his letter. A couple of weeks ago they met for 3 hours and Barr was seen leaving the White House with his head down. I think it was all settled then. It was a kiss @ss letter detailing all Trumps accomplishments. It looked too carefully written. And it was probably approved by Trump before he let Barr leave gracefully.