Mostly, but not entirely. Under the "Impact on Amazon Relational Database Service (RDS)" section they state that due to two other bugs, some Multi-zone RDS inst

Mostly, but not entirely. Under the "Impact on Amazon Relational Database Service (RDS)" section they state that due to two other bugs, some Multi-zone RDS instances did NOT fail over, because their systems knew that the masters had stopped replaying to the standbys, but had continued to process some transactions (albeit more slowly, as the failures cascaded and amplified), and thus prevented the automatic promotion of a standby, as the standbys were now out of date.