The default policy for UpdateRequest and DeleteRequest is NO_YIELD, which is dangerous (see SERVER-47699) and should be opt-in, not the default. Additionally, most users of UpdateRequest and DeleteRequest already override this default. Examples:

• https://github.com/mongodb/mongo/blob/7cc71f7d5f29a5850a4d186b9554df3dcb407117/src/mongo/db/update/update_util.cpp#L168-L170
• https://github.com/mongodb/mongo/blob/7cc71f7d5f29a5850a4d186b9554df3dcb407117/src/mongo/db/commands/write_commands.cpp#L571
• https://github.com/mongodb/mongo/blob/7cc71f7d5f29a5850a4d186b9554df3dcb407117/src/mongo/db/commands/write_commands.cpp#L749