No it's not; how are EVs acquired, if not by vitamins? PKHeX only recently added a simple "nonzero EVs" sanity check, where to have any non-vitamin EVs, you should have gained experience as well. The amount of experience (minimum amount) isn't easy to calculate and isn't worth the time.
The batch editor can be used to bump EXP easily with the improvements made in the past year:
.CurrentLevel=30
-EXP=1
The above batch instruction sets all levels to 30, then decrements EXP by 1 (reducing its level to 29.9999). Useful for nuzlocking. You can do similar for adding EXP (using + instead of -), but again, just adding 1 EXP is not a "legal" workaround because 1 EXP is not enough for gaining many EVs.
The error message is pretty clear if you think about it