Thanks, Justin.
That's what I ended up doing - adding 0 margin.

I'm not sure if this CSS will come through in the comments, but the blockGap is added with the CSS below, and it actually added 2 sets of 24px to the top of the sections (24px is the Gutenberg default). Anyway, I'll get the CSS all organized the way I want eventually.

.wp-site-blocks > * + * {
margin-top: var( --wp--style--block-gap );
margin-bottom: 0;
}