You may present a bull or a lamb that has a part too long or too short for a freewill offering, but for a vow offering it cannot be accepted.
Leviticus 22:23

Biblical freewill offerings aren't owed to God, so can have a single minor defect, e.g. a limb shorter than the others. On the other hand, vow offerings *are* owed and must be perfect. Giving God an imperfect vow sacrifice is like using unequal weights in trade. Don't cheat God.

Improperly performing God's prescribed rituals profanes his name. Actions have consequences. Correct understanding is good, but correct doing is better. (See v32.)