ConstExported for a host aligning something to the INPUT of a field whose helper line is collapsed
(helperText: null): the block is no longer symmetric, so its middle is no longer the input, and
align-items: center on the row would sit that high by exactly this much. Pad the sibling by this
and center it in what is left. With the helper line RESERVED (the default) nothing needs it.
The height an
'above'label adds over the input — its line plus the gap under it.