It's not just BA. AA does as well. While EC 261/2004 does apply to departures from the EU for AA, the scenario AMS-LHR-JFK where the first segment's delay causes a delay to the second segment triggering Type 3 rather than Type 1 compensation won't happen to AA because it does not (may not) operate the initial short-hop which causes this problem.

Moreover, unlike BA and almost all other carriers, AA does rebook across separate AA-AA, AA-OW, and OW-AA tickets. While the COC provision offered by AA is not protection in the full sense, one does get rebooked, which is an awful lot better that having the onwards ticket cancelled.

Nonetheless, AA will not check bags across tickets, even AA-AA.