Does initial signup require a reward attached to it?

Let's say I have 3 levels, A, B, C.
I also have indefinite rewards setup so affiliate plugin will track not just the first purchase but all of them.

There is no reward for affiliates for level A.
B and C levels have a reward.

What happens if a customer signs up for a blog at level A, then a couple months later switches to level B or C. Will it just work?

I'm afraid that since level A doesn't have a reward that it will not trigger the affiliate to receive rewards.
Then later if a customer switches to a level that pays out a reward the affiliate will not get credit because it never triggered the system to reward them from the initial signup.

Just want to run this by you guys and confirm how this works under such circumstances. I'm interested in level A not having a reward attached to it.