What is wrong with one pool? It lists way different

[hput]

Normal "zfs list -r rpool"  show the expected (abbreviated) view:

[...]
rpool/ROOT/ubuntu_7sgaqg/usr                      2.27M   266G       96K  /usr
rpool/ROOT/ubuntu_7sgaqg/usr/local                2.18M   266G     2.18M  /usr/local
rpool/ROOT/ubuntu_7sgaqg/var                      2.01G   266G       96K  /var
rpool/ROOT/ubuntu_7sgaqg/var/games                  96K   266G       96K  /var/games
rpool/ROOT/ubuntu_7sgaqg/var/lib                  1.99G   266G     1.82G  /var/lib
[...]

Above: Just what one expects:

But another pool (p0) lists absolutely different:

[...]
p0/reader at 2x-20220614081902     1.12M      -     5.25G  -
p0/reader at 2x-20220614.224349    32.2M      -     5.23G  -
p0/reader at 2x.f0-20220616131053  33.5M      -     5.23G  -
p0/vb                            473G  1.28T     18.5G  /vb
p0/vb at 220520                      64K      -     18.5G  -
p0/vb at 2x-20220526233254           64K      -     18.5G  -
p0/vb at 2x-20220527145415            0B      -     18.5G  -
[...]

Appears to be displaying all snapshots??

This happened after exporting all pools in preparation to install
22.04

Once the install was done I imported the pools.  Seemingly smoothly:
no errors

Have I managed to set/unset something in the pool to cause this?

Any other reasons why a pool would display in such a different way?