Sure it did. In the 1910s Congress' Commerce Clause powers wouldn't have encompassed purely intrastate commercial activity. The legal landscape was already changing, slowly, but in no way would a national law have been effective without a constitutional amendment. Heck, at that time the Supreme Court interpreted the ratified Prohibition Amendment not to apply to homemade liquor for personal consumption, despite the plain text of the amendment.[1] Compare that to Gonzales v. Raich (2005) where the Supreme Court permitted Congress to regulate, under Commerce Clause powers alone, homegrown marijuana for purely personal use.

Perhaps the line of reasoning you're alluding to is that, at the time, state and local prohibition laws were already so common that the Prohibition Amendment shouldn't have changed the effective legality of alcohol consumption for most Americans. But to maintain the status quo in perpetuity, locking in Temperance Movement reforms without defectors slowly eating them away, a national law was desirable.

[1] I'm still looking for the citation, but IIRC the reasoning was that the court wouldn't interpret the amendment to reach private, non-commercial activity unless it was explicit on that point; it wasn't just a cop-out textualist dance with the word "manufacture".