would this 'error' not be similar in nature to the 'nils' error I was puzzling over?
nils error? Are you referring to the Lynn Allen thread?
If so, then no.
Since (vl-load-com) only needs to be called
once per drawing session to load the Visual LISP extensions, it makes sense to include it in the ACADDOC.lsp and not in every program (in which every subsequent call to the function is redundant). However, this more efficient approach may confuse beginners who don't include it in the ACADDOC.lsp or have not experienced errors similar to that described above.
The 'nils' returned by a program is
not an error, but merely bad practice when writing a program called from the command line. Note that some functions may
intentionally return nil to serve a particular purpose.