j2j7 doesn't seem all that decisive. ChessV does like to respond to it likewise (a9a4), but other responses seem OK. I tried a black response if f8e6, then let ChessV compute on this for 15 minutes, reaching a search depth of 23. It responds with j7b7, threatening the Marshall, and thinks white has an 1/8th pawn advantage. So there may be some advantage, and certainly some harassment potential, but it doesn't seem too bad.
j2j7 doesn't seem all that decisive. ChessV does like to respond to it likewise (a9a4), but other responses seem OK. I tried a black response if f8e6, then let ChessV compute on this for 15 minutes, reaching a search depth of 23. It responds with j7b7, threatening the Marshall, and thinks white has an 1/8th pawn advantage. So there may be some advantage, and certainly some harassment potential, but it doesn't seem too bad.