Anshul, sorry this is a bit late. I'm not sure why it is changing the sort on you, I've captured the issue so we can look into it further.
But in the meantime I have a workaround for you.
If you created a calculated field for your aggregation and drag that to rows, the sort should be what you are expecting. I tried a calc field for both sum([Gross Fraud BPs]) and avg([Gross Fraud BPs]) and both gave me the same sort order on Copy > Data > Paste in Excel.