I guess the answer is both times no ;)
It is not a bug and you are not doing the export incorrectly - the excel sheet is not ordered by impact, and thus maybe the higher contributing processes that you miss are hidden in the screenshot? Or, could you post a picture with the "top contributor bar chart" and the corresponding columns in excel? As e.g.
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(a bit small, but the top contribution in aquatic ecotoxicity is reported with the same amount in excel).
Best wishes, thank you,
Andreas