there is a 2 way blade could have smile.
1 is blade has been made that way.
in this case spine is even from tip to the heel . Usually you don't have to do anything.
2 case is a little different.
blade have smile face because of honer.
he may do this intentionally or unintentionally end result doesn't matter.
Spine has more hone wear compare to middle and heel side of the blade.
Now everything depends how much hone wear spine has.
if it is very little then strop will cover it. you don't have to worry about it again.
If there is too much hone wear on the spine then you may try to use x patter strokes on your strops.
hope this helps.