Only if you apply the same tag to all rock art that doesn't have a context to date it :-)
Some of the smaller, portable ones are probably early Christian, but the multiple & earthfast examples (most probably) aren't.
As StoneLifter commented below, many of the smaller portable ones do appear to be cut from a larger piece of rock. The common belief (mainly pushed by me I admit) is that the use of bullauns in church yards is a very good example of the early church in Ireland absorbing an older religion to fight it.
A great many of them have St. Brigit associations, which points to them (possibly/probably) being associated with the celtic Brigid beforehand.