We would argue that the 39 Articles were not a firmly Calvinist / reformed Protestant document but rather a carefully crafted compromise that can be interpreted in a manner that could be sold to both Catholics and Puritans.
The Articles are general enough that Reformed and Anglo-Catholics could (and still can) abide by them. However...arguably, 16th Century Catholics (like most 16th Century Christians actually) were more predestinarian than modern Catholics (and generally, modern Christians of all types) tend to be.
The popular use of "Calvinist" today usually is shorthand for predestinarian, and the 39 Articles definitely are that.