pt-archiver keeps transaction open while waiting for replica to catch up

-- give master some advantage on performance
SET GLOBAL innodb_flush_log_at_trx_commit=2;
SET GLOBAL sync_binlog=1000000;
SET GLOBAL innodb_buffer_pool_size=2*1024*1024*1024;
USE test;
 
DROP TABLE IF EXISTS `joinit`;
 
CREATE TABLE `joinit` (
 `i` int(11) NOT NULL AUTO_INCREMENT,
 `s` varchar(64) DEFAULT NULL,
 `t` time NOT NULL,
 `g` int(11) NOT NULL,
 PRIMARY KEY (`i`),
 KEY g_idx (g)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO joinit VALUES (NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )));
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit;
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; -- +256 rows
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; -- +512 rows
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; -- +1024 rows
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; 
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; 
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; 
INSERT INTO joinit SELECT NULL, uuid(), time(now()), (FLOOR( 1 + RAND( ) *60 )) FROM joinit; -
...run few more so it has a few million rows

SET GLOBAL innodb_flush_log_at_trx_commit=1;
SET GLOBAL sync_binlog=1;
SET GLOBAL innodb_buffer_pool_size=128*1024*1024;

PTDEBUG=1 ../pt-archiver --purge --where "g < 45" --commit-each --limit=500 --statistics --source "h=localhost,S=/tmp/mysql_sandbox19731.sock,D=test,t=joinit,u=msandbox,p=msandbox" --check-slave-lag="h=localhost,S=/tmp/mysql_sandbox19732.sock,u=msandbox,p=msandbox" --max-lag=10 > /tmp/pt-archiver.debug 2>&1

---TRANSACTION 4287278, ACTIVE 2 sec
2 lock struct(s), heap size 1136, 1 row lock(s), undo log entries 1
MySQL thread id 45, OS thread handle 140647079315200, query id 15158693 localhost msandbox
Trx read view will not see trx with id >= 4287278, sees < 4287278

sysbench --mysql-host=127.0.0.1 --mysql-port=19731 --mysql-user=root --mysql-password=msandbox --mysql-db=test /usr/share/sysbench/oltp_read_write.lua --tables=100 --threads=6 --table_size=100 --time=1000000 --report-interval=1 --db-ps-mode=disable --range-size=9205 --skip-trx=false --point-selects=0 --simple-ranges=0 --sum-ranges=0 --order-ranges=0 --distinct-ranges=0 --index-updates=3 --non-index-updates=0 run

~$ while true; do { ./use -e "SHOW ENGINE INNODB STATUS\G"|grep History; sleep 1; } done
History list length 174403
History list length 186116
History list length 191834
History list length 193754
History list length 194419
History list length 195433
History list length 199125
History list length 203649
History list length 213459
History list length 222541