You've completely missed the point of my post. Let's take it slowly.
Your premise is that they are lacking calls, as their only caller is on tank where he is unable to call well.
They decide they need a calling Lucio, so they need to cut someone to pick one up.
Rather than just cut art1er and move roles around, or indeed cut anyone else on the roster (leading to an overall increase in comms) they chose to cut their former caller. They could have kept a caller on tank AND lucio if the comms were the only problem.
Why remove the tank, who was calling, rather than any other quiet player to make room? If comms were the only reason to make the move, as you say, then this premise makes no sense and would be detrimental. There were clearly reasons outside of "not enough calling from seb" to make the switch.
Even ignoring this entire problem, your argument so far is that his calling was hampered by his position on tank - so why would it be a bad move to pick him up as a caller on Lucio?
...And time will tell whether picking a calling Reinhardt is good or bad.
He's not gonna be calling from Reinhardt! If you think his calls were bad that's another thing entirely, but so far you've said nothing worthwhile about the actual acquisition because your entire premise is based on him playing tank and lacking quantity rather than quality of calls.