In general, airlines will not match from any program in the same alliance.

This is because your existing program status already gives you similar/most of the benefits that your requested status would.

There is no need to change programmes just because you are moving, particularly if it's only a temporary move. Even if you do want to start collecting in the Flying Blue programme (and if you are not familiar with the programme, it's not a particularly good one) you can still use your Delta card to claim benefits while earning to FB.

But only switch to FB if you know exactly what you are doing, and have a really good reason for doing so.