Clickhouse open source and cloud user. My understanding is that the cloud version uses S3. Which would mean that they have very specific tenant pattern and code to run that version. This may be why lightweight work a specific way in that environment, or they need a way to test it at scale that would be hard through a feature flag in the open source product. Lightweight deletes were released to both, and previous roadmaps listed updates as upcoming.

You should be using ReplacingMergeTree if you are doing updates at the current moment.