I will give my input based on my experience giving final rounds at a tier 2 firm as well as my own experience moving to MBB.
First of all it's important to take official feedbacks with a grain of salt.
(1) For legal and marketing reasons firms are very careful regarding the feedback they provide. I've been part of final round discussions with partners were we discussed interviewee's attire, the fact they have spouses or not, age, ... for obvious reasons we won't say that we didnt hire someone because you wore the wrong sweater.
(2) Depending on the season/office/position you apply the demand for new hires will be different and that will impact the threshold for giving an offer. A common myth is to think MBB will always hire regardless of their needs. I've discuss with a MBB partner that putted very blunt "at this period in the year we have reach our target quota, anyone can still apply but they will only be hired if they are a superstart, otherwise waiting until January is better."
Now, this is not to say that you should disregard your feedback. You have mention a specific point that you could focus on.
If I was in your shoes I would do the following:
1) Status quo. What other firms are you currently in process, what firms could you potential still apply and what is the timeline to do so
2) Honest assessment. Get an unbiased opinion on where you currently stand today. This means, PEI, case, Q&A, ...you only know how much work do you need to do if you know where you stand
3) Develop a "work plan" for the remaining of your time taking into account the feedback you received
Happy to discuss this on a call if you would like