the best explanation of that limitation is found in the suitescript help page:

In the NetSuite UI, only certain fields are inline editable. These are fields that have no slaving relationship to other fields. When users update a field that is inline editable, only the data for _that_ field is updated; there is no cascading effect on other data contained in the record.

That's really good to know, didn't know about that. Need to double check this also always. Thank you!