Just to update my own post here, I'm reading up of the DFT circular that seems to reference these bus gates.
One point I note is section 9.7.3.
A bus gate is a short length of bus‑only street. On a two‑way road, access may be
restricted to buses in one direction only, with all traffic permitted in the opposite direction, i.e.
similar to a contraflow lane, but too short to be signed as such. In this case, that part of the
carriageway reserved for buses should be separated from the opposing flow of traffic by a
traffic island and not by a continuous line marking to diagram 1049A (see Figure 9-25). Bus
gates are often used to remove through traffic from a road but allow full access. They effectively
create a “no through road” for all traffic other than buses. The bus gate may be located either
at a junction or part way along a road, and may be used by other vehicles where permitted by
the order.
If a bus gate is placed on a road that was previously a signed route or was used by
significant through traffic, consideration should be given to providing or changing directional
signing to guide prohibited traffic to use the preferred alternative route, as described in 5.1.2.https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/782724/traffic-signs-manual-chapter-03.pdfI'd argue that the lack of warning about the Bus Gate, the incorrectly painted arrows directing you to the Bus Gate lane and the update from the previous design (which was in use up until 2018 as I have screenshots showing this) shows that this consideration has not been taken.