In this simple test, why does Athena fail to prune partitions?

I have defined two tables:

CREATE EXTERNAL TABLE `event_data`(
  `systemid` string COMMENT 'from deserializer', 
  `eventtime` string COMMENT 'from deserializer', 
  `eventtype` string COMMENT 'from deserializer', 
  `source` string COMMENT 'from deserializer', 
  `updtdate` string COMMENT 'from deserializer', 
  `rawdata` string COMMENT 'from deserializer', 
  `media` string COMMENT 'from deserializer')
PARTITIONED BY ( 
  `partition_day` string)
ROW FORMAT SERDE 
  'org.openx.data.jsonserde.JsonSerDe' 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.mapred.TextInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION
  's3://test-bucket/incoming/data/'
TBLPROPERTIES (
  'classification'='json', 
  'projection.enabled'='true', 
  'projection.partition_day.format'='yyyy-MM-dd', 
  'projection.partition_day.range'='2010-01-01,NOW', 
  'projection.partition_day.type'='date', 
  'storage.location.template'='s3://test-bucket/incoming/data/${partition_day}/')

and

CREATE EXTERNAL TABLE `event_index`(
  `systemid` string COMMENT 'from deserializer', 
  `eventtime` string COMMENT 'from deserializer', 
  `eventtype` string COMMENT 'from deserializer', 
  `source` string COMMENT 'from deserializer', 
  `updtdate` string COMMENT 'from deserializer', 
  `partition_day` string COMMENT 'from deserializer')
PARTITIONED BY ( 
  `partition_year` string)
ROW FORMAT SERDE 
  'org.openx.data.jsonserde.JsonSerDe' 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.mapred.TextInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION
  's3://test-bucket/incoming/index/'
TBLPROPERTIES (
  'classification'='json', 
  'projection.enabled'='true', 
  'projection.partition_year.format'='yyyy', 
  'projection.partition_year.range'='2010,NOW', 
  'projection.partition_year.type'='date', 
  'storage.location.template'='s3://test-bucket/incoming/index/${partition_year}/')

then I inserted some data into partitions 2024-03-09 and 2024-03-11 and ran some simple test queries:

select * from event_data where partition_day = '2024-03-09'

select * from event_index where event_index.updtdate <= '2024-03-10'

SELECT * FROM event_index JOIN event_data USING(partition_day, systemid) where event_index.updtdate <= '2024-03-10'

By looking at the "Data scanned" metric when querying in the console, I can see clearly that partition pruning works fine with the single-table queries, but degrades to full table scan in the JOIN query.

Why is that (not) happening?

EDIT: if I simply swap the order of tables in the JOIN, the partition pruning happens as expected.

EDIT2: If I put the query with the swapped JOIN into a View, then the pruning fails again, so I'm back to where I started.