What is op expect in stdin?

$ op --version
0.8.0

When I use "op get" in a loop, it looks like it consumes all of my stdin, which breaks the expected behaviour in the loop.
Why is that?

Context setting:

I created two login items as below (printed the title and UUID using jq)
$ op list items | jq '.[] | select(.overview.title | test("XXX")) | .overview.title,.uuid'
"XXX"
"o4rhpeihtfhrvcsfandstpmm5a"
"XXX 1"
"j5ug6csxmbbhpmzza7akxio3ru"

I can read and dump the values in a loop as below:
$ op list items | jq '.[] | select(.overview.title | test("XXX")) | .overview.title,.uuid' |
while read t; read u; do
u=$(echo $u | sed 's/"//g') ;
echo "$t\t\c" ; echo "$u" ;
done
"XXX" o4rhpeihtfhrvcsfandstpmm5a
"XXX 1" j5ug6csxmbbhpmzza7akxio3ru

When I try to process with op, the stdin data is consumed...
$ op list items | jq '.[] | select(.overview.title | test("XXX")) | .overview.title,.uuid' |
while read t; read u; do
u=$(echo $u | sed 's/"//g') ;
echo "$t\t\c" ; echo "$u" ;
op get item $u >/dev/null ;
done
"XXX" o4rhpeihtfhrvcsfandstpmm5a

If I redirect stdin for op, then things get back to normal.
$ op list items | jq '.[] | select(.overview.title | test("XXX")) | .overview.title,.uuid' |
while read t; read u; do
u=$(echo $u | sed 's/"//g') ;
echo "$t\t\c" ; echo "$u" ;
op get item $u >/dev/null </dev/null ;
done
"XXX" o4rhpeihtfhrvcsfandstpmm5a
"XXX 1" j5ug6csxmbbhpmzza7akxio3ru

What is happening here?

Initially I chalked it ot catalina vagaries, but this is universal.