המשליך (throw/cast) is from a distance. (Also associated with this verb is the concept of despair and leaving.) If it is placed quietly on the ground, it will say מניח or משים or נותן.

And when Tosafot⁶⁵⁸ says that ordinary השלכה (throwing/casting) means at least twenty amos, it is only talking about when the priest casts away the crop of a bird with its feathers⁶⁵⁹.

footnotes: ⁶⁵⁸ Babylonian Talmud Meilah 11b. ⁶⁵⁹ Leviticus 1:16.