What's the stock bore on a GSR block phatintegra?
On a B18a1/b1 it's 81mm, you don't need to resleeve to go to 81.5. Hell I would even be comfortable going 82mm, anything 83mm or above I would resleeve personally. But .5mm isn't really much at all to worry about.
To the OP:
Unless YOU ordered the wrong rods, or for some reason swapped out the crankshaft, there should be no issue with the stroke. Get your block back and say you'll have somebody else do the work. Don't lie to them and say your going another way- straight up tell them that you think they're full of shit and you want your motor back.