Shelltron and critical attacks.

[Reynhart]

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.

Well, the order is completely arbitrary, so it makes as much sense as any other order.

You could very well check first if the hit connected properly (so, no dodge, no parry, no block), and after, you have a chance to apply critical damage.

Also, in that case, if the hit crits, the game won't check for block, so you won't reduce anything.