I suppose that could be extrapolated as the meaning, but the word translated "unwholesome" is the Greek
sapros, which is defined thusly: rotten, putrefied; corrupted by one and no longer fit for use, worn out; of poor quality, bad, unfit for use, worthless.
That definition would more appropriately define course, crude, disgusting language. The world has long had curse words and that is specifically what Ephesians 4:29 -- the only verse in which
sapros is translated "unwholesome" -- is speaking about. A confirmation of the meaning behind the word is found in the good doctor's writings:
Luke 6 NASB
43 "For there is no good tree which produces bad fruit, nor, on the other hand, a bad tree which produces good fruit.