Your question is a good follow-up.
First, please let me point to the second sentence of #6 (on page 7) under Additional Guidelines of the Guidance for Transcription Using the Nemeth Code in UEB Contexts, which says "When table entries are technical material but the row headings are words, the whole table is considered technical material, excluding the table title and column headings." Dorothy Worthington used the example you shared (thank you for uploading it) to illustrate this portion of the Guidance.
Second, you're right that Laurie could have used what's outlined in #6 mentioned above to lay out the "Account Balance" table. An image of the braille for this layout is attached.
Third, the Guidelines and Standards for Tactile Graphics currently do not include anything on using Nemeth Code within UEB contexts. So, we are left to make the most reader-friendly decisions we can within existing code guidelines. With that said, unless it would be confusing, I agree with your assessment that (until/unless TG Guidelines tell us otherwise) labels for the axes of a graph presented as a tactile graphic could be included uncontracted within Nemeth Code switch indicators that are necessary for the rest of the graph [This is not the case for Laurie's graph if only the dollar sign is done away with].