The bug
When doing /setblock ~ ~ ~ redstone_wire, it sets the block in its dot form and not the new + form.
MC-193494
/setblock redstone_wire sets the block for the redstone dot
Resolved
Works As Intended
2
You need to specify a block state when doing setblock or fill if you want the block to reflect that blockstate. Typing;
/setblock ~ ~ ~ redstone_wire[east=side,north=side,south=side,west=side]
will give you the one you want.