The comment in this piece seems generally factual to me. Yes, the WA and the TCA were poor for the UK but the guts of the first one were little to do with Lord Frost, who entered the fray late on and was assigned the task of making the best job he could of modifying May's "Chequers Agreement", which was the only way to get any agreement with the EU. Critical elements of the WA were demanded by the EU and only modified by the UK, from May's midnight flit to Germany, probably had to have Merkel's blessing.
The TCA was relatively rushed but Frost was under pressure from Johnson to "get Brexit done". Negotiations with the EU were already known to be lacking in the good faith department anyway and the clock was running.