Putting the question in the context of the regulation ...
(1)Political relationship means a close identification with an elected official, a candidate (whether or not successful) for elective, public office, a political party, or a campaign organization, arising from service as a principal adviser thereto or a principal official thereof;
In shorthand, your argument is that it is a gray area whether or not Jeff Sessions had a political relationship with the Trump campaign. I take it your conclusion is that Jeff Sessions did NOT have a political relationship with the Trump campaign.
I don't think the recusal is a close question. Sessions' impartiality with respect to the Trump campaign can reasonably be questioned.
In cut throat DC politics, however, where everyone is out to kill the king, "principal" advisor could be debated. Principal endorser might be accurate.
It's all in the rear-view mirror, though, isn't it.