Union Ballot - 5 motions - only entitled to vote on 3

I for a public sector employer and we had a union ballot today on what I thought was 5 motions. However, when I got to the polling room, the shop steward asked me what part of the organisation I worked in and I was presented with 3 ballots and was told that the other two ballots only applied to the "Type A" members and therefore I could not have a ballot paper for motions 4 & 5. The "Type A" members will be able to vote on all five motions.

I found it unusual that Union members were being split into different groups. Is the whole idea of a union not solidarity? Has anybody else come across this situation where not all the constituency can vote?

Motions 1, 2, and 3 will impact on all groups ("Type A"s and "Type B"s) but if one of these motions is not covered "Type A"s will still have their own motions to fall-back on.

Can you explain A and Bs.

If it is Contract related , A has in contract , B has not thats acceptable.

As long as there is no knock on impact to B .I.E Industrial action on A behalf by B.