You're correct Peggy, that there is some misalignment between the current versions of GSTG and BF. As you suggest, this arises in part from the fact that the current versions of these documents were published at different times.
Because of the complexity of creating and reading maps that may cover several braille pages, the key MUST be intuitive to assist in remembering the key over multiple pages. Tables are not usually as complex as TGs, and have the option of being condensed, shortened, or abbreviating before opting to use a key. However, tactile graphics do not have the luxury of space that benefits the transcription of a table.
Keys in TGs are limited to only 2 or 3 braille cells, and often use the first letters of a word, as in "bl" for Black Sea. To differentiate, if the transcriber was using the letter “o” for all of the ocean names, they may use "ao" for Atlantic Ocean, and the contraction "aro" for Arctic Ocean. Similarly, some transcribers try to use the letter “r” as the 2nd letter for all of the rivers on a map. Sometimes, but not always, this helps give the reader an additional clue.
Now back to the crux of your question. If a transcriber chooses not to use any short forms (based on Braille Formats) that is acceptable, as long as they are not changing those specified in GSTG Appendix C. We have been advised that the forthcoming updates to Guidelines and Standards will not restrict the use of contraction.
So, until the documents are synchronized, we recommend that your TGs containing maps and map keys must follow the International Organization for standard abbreviations and use of two-letter symbols as specified in GSTG Appendix C. This comes with the realization that in some cases the resulting key symbols will not contain a dot 3 and/or a dot 6 (GSTG section 184.108.40.206).
We are keen on ensuring that you have the information you require, so please let us know if this answers your question!