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Can you buy gift cards at grocery store to receive a higher reward rate?
Understand that buying a Starbucks gift card at the grocery store to receive 6% back on your coffee rather than 6% back on your groceries is an exploit of a flaw in the benefits program, not a feature.  It's definitely not a blanket yes or no answer, the only way to find out is to try. Separately, I don't know why you would find this "concerning."  This will vary greatly between merchants and cards.  There will always be new points churning exploits, they don't last forever and you can't expect every customer service rep to be well versed in methods employed to juice cardmember programs. Hell, a number of years ago one person figured out that he could buy rolls of $1 coins from the US treasury with free shipping and no additional fees.  This guy was literally buying thousands of dollars of cash each month to deposit and pay his credit card bill; completely against the terms of the treasury program for distributing the $1 coins.  A number of people had their cards and points/cash back revoked for that one.