@0x666 thanks for flagging this. Excluding all Monorepo contributions is not the intention of this rule, its intention is to only support contributions from core devs. This is done to avoid creating an incentive for low quality PRs & issues because reviewing those requires significant time and care of the core devs. Other projects have experienced this situation where possible rewards lead to the creation of a large number of low quality PRs & issues and we want to avoid that pitfall.
The language in the round 5 forum post has been updated to reflect this
Only Optimism Monorepo contributions by core devs may be rewarded within Retro Funding 5. Commits to the monorepo are currently mainly done by Optimism core devs and the core dev program is not developed enough to support outside contributions to the monorepo yet. As the core dev program evolves, more contributions to the monorepo may become eligible.