It is a set of historical accidents, and shows it. A better source for standard mnemonics might be the NIC site codes, since these have been chosen with more care and will become familiar as we begin to use the NIC on-line. Surely the NIC is a more reasonable source for a defacto standard than a particular system programmer. You show only 20. Your proposed standard should include known hosts at this time.
Standards are vital, and deserve a little care.