Idiom for dismissing collegue's correction in first place, but heeding, acting upon when management says to do it

Question

Context:

Jack has total 15 years experience, 12 years experienced in a company XYZ, Jim has total 15 years experience in same field as jack but 10 years in XYZ. That makes Jack a senior to Jim technically. But in Jim's head, he thinks he is equal to Jack.

Now the situation is Jack is given a project to execute and assigns Jim to do a part of it. Jim gets the planning dept involved to prepare some bar charts for his part. Upon finalizing the barchart with the planning dept, Jim submits the chart to Jack. While reviewing it Jack finds missing links and tells Jim to correct it. Jim (thinks jack is bossing) diplomatically dismisses as if it is trivial thing and does not need to be corrected.

Now after a few hours. Jack, Jim are called in for a meeting with management. The managements discusses a lot of other things. Jack highlights the trivial thing that Jim has dismissed about the bar chart without pointing finger \at jim's reluctance. The management reacts saying it is important to get it changed because the management will be owned by the Client during their meeting with what ever trivial matters there is in the chart.

Jim come out saying true that this is an important point and has to be addressed.

Now the question is What is Jim doing when he dismissed the issue as trivial when a only one year sr. colleague asked him to correct it, but when management remarked he came up saying it was right thing to do and made up an idea to correct it as if he has thought it through all along.

PS: Thing is if management is owned by the client, they will question Jack and not Jim. (if thats necessary for context)

Example:

Jack to John: In the meeting Jim was some one else, I could n't believe he ___________ (spoke contrary to what he was saying to me)

Answer 1

This doesn't quite fit the specific description but a general term could be saving face.

Jim didn't react when Jack pointed out mistakes in the work, but when the manager noticed, Jim was saving face by agreeing to fix it.

Answer 2

There is this idiom "(a) volte-face" which implies complete reversal of an earlier stance.

In the meeting Jim was someone else; I couldn't believe he did a volte-face.

TFD(idioms):

volte-face
A complete change of opinion or belief. The phrase comes from the Italian term voltafaccia.
Everyone was surprised when the candidate made a complete volte-face on her stance on taxes.

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