Shelltron and critical attacks.

[Shurrikhan]

That's simply how the game is coded and it makes sense.

Is damage crit? Yes
Did target block? Yes
Take Crit damage number, reduce block percentage, apply damage.

No, it's not, and no it doesn't particularly make sense.

The sequence is

Crit: Yes/No

If yes:

Damage crits. It cannot be dodged, blocked, or parried.

If no:

Dodge: Yes/No

If yes:

All damage is avoided. It cannot be blocked or parried.

If no:

Block: Yes/No

If yes:

Damage is blocked. It cannot be parried.

If no:

Parry: Yes/No