I just very recently read that BA-coded flights operated by other airlines on a oneworld RTW ticket can earn distance-based TP rather than spend-based. However, reviewing my flights from the past year (since April), all the RTWs issued NOT by BA, some segments earned distance-based while some were spend-based. Any idea why the difference?

Does it depend on whether the flights were taken right after the first issuance of the RTW (hence clearer spend?) vs reissuance later obscure the fare details, triggering distance-based earning for subsequent flights?