User defined variable not recorded into context

create or replace table t1 (

  x int unsigned,

  y int unsigned

) with system versioning;

create or replace table t2 (

  x int unsigned,

  y int unsigned

) with system versioning;

insert into t1 values (1, 1), (1, 2), (1, 3), (4, 4), (5, 5);

insert into t2 values (1, 2), (2, 1), (3, 1);

set @t0= now(6);

delete from t1;

delete from t2;

explain extended select * from (select t1.x as IJ2_x1, t1.y as y1, t2.x as x2, t2.y as y2 from t1 inner join t2 on t1.x = t2.x)

for system_time as of timestamp @t0 as t;

drop table t1,t2;

./mtr example.test  --replay-server