End Bricks have very low blast resistance

End Bricks seem to have very low blast resistance.

I tested a 5x5x5 of End Bricks against other materials, placing a block of TNT in the center, and for every other type of "stone" I tested (stone, stonebricks, purpur, purpur pillars etc) the TNT blew up a 3x3x3 inside. However when tried with the End Bricks, almost the entire 5x5x5 blows up, leaving a few of the corners.

I just thought it's weird how End Bricks have much less blast resistance than regular End Stone, so I figured it must be a bug / mistake.