The Polish mathematicians deserve a lot of credit, and more than they tend to receive. Turing tends to get almost all the plaudits these days, perhaps also out of guilt about his personal story, the circumstances of his death, his persecution for being gay and so on; and, in the process, his colleagues and his predecessors are overshadowed. But Turing would certainly have been the first to say it was a team effort. It's perhaps also a failing that we are desperate often to find *one* person to praise, rather than an entire organisation (see also the Nobel prize, which is still limited, outside the Peace award, to no more than three individual recipients in spite of the fact that this is completely unrepresentative of modern science).
Another reason is that just in general the contributions of Poles to the war effort tended to be ignored for political reasons at the time. For example, the Polish pilots in the Battle of Britain were not invited to postwar celebrations, despite as high an authority as Dowding praising their vital contribution.
https://en.wikipedia.org/wiki/No._303_Squadron_RAF
So in this respect, I wouldn't be surprised if there's some level of, sadly not unjustified, bitterness on your friend's part, motivated by this history.