Michael H Deckers via tz wrote:
Why not just avoid every proleptic use of WITA
Thanks for your thoughtful comments. We don't know when acronyms like WITA started to be used, so we don't know which usages are proleptic and which are not. In the absence of information I was reluctant to insert arbitrary transitions that change only abbreviations, as that would indicate a degree of knowledge greater than what we have. More generally, the tzdb does not strictly attempt to avoid proleptic abbreviations. Common abbreviations like "CET" are proleptic when used for 100-year-old timestamps, and tzdb does this routinely.
My other concern is the removal of the acronym JST for UT + 09 h in favor of +09 when used in occupied territory.
JST wasn't removed everywhere, only in areas that typically use numeric abbreviations. The idea was to use JST in occupied regions like Asia/Hong_Kong that have alphabetic traditions like HKT, and to use +09 in occupied regions like Asia/Yangon which lack such traditions. That way, historical tables in these areas will tend to use a consistent style, which is a plus. Some of the previous tables' JST transitions were dubious anyway. Was it really called "Japan Standard Time" in Jakarta on September 22, 1945? And why wasn't "JST" used for Asia/Jayapura during 1942-1944 when Jayapura was at +09 and was under Japanese Imperial control? It was too much trouble to decide when to use JST vs +09, and it was a relief to remove this questionable political trivia when possible. In an attempt to better document the above, I installed the attached proposed patch.