The station is referred to as 'Old Yau Ma Tei Police Station' in multiple government sources (e.g. https://www.info.gov.hk/gia/general/202512/26/P2025122500592.htm), with the 'old' capitalised in running sentences, indicating that it is not merely a description but a formal name. From a rendering POV, the 'Old' is also necessary to differentiate it from the 'new' YMT Police Station just a stone's throw away.

You’re asking about a changeset made 12 years ago and apparently I couldn’t recall the circumstances. I guess MTR did advertise B1-B4 exits at some point before they were replaced with a simple B. FYI B1-B4 are shown in the Buildings Department’s railway protection boundary maps: https://www.bd.gov.hk/doc/en/resources/codes-and-references/ScheduledAreas/MTR-RP-59.pdf