In the description of the law, how is that meaningfully different from promising tax policy changes?

It’s not telling people to vote, not vote, or to vote for anyone in particular, and is just a notification of something they’ll do if elected.
The implication is that you should vote for them, but you didn’t make the offer conditional.

Bribery is easier if you’re using other people’s money because rather than paying people to do what you want you can make a blanket promise to everyone and let them work through the implications.