"GIT_STRATEGY: none" isn't respected in review-apps pipelines

Context

As part of !108140 (merged) (and earlier on in #357542 (closed)), we have noticed that setting GIT_STRATEGY: none has no effect in certain jobs.

After some investigations (I'll post them in discussions in this issue), the jobs in the review-apps child pipeline are affected.

Affected jobs

See this search

Goal

Find out the problem, and ensure we can use GIT_STRATEGY: none in the review-apps pipeline.