Silverfish blocks (Monster Egg Blocks) do not spawn silverfish w/ silk

When mining with diamond silk pickaxes, silverfish eggs (noted because the block takes longer to mine) do not spawn silverfish, drop an ordinary block. Using a non-silk pick-axe, silverfish spawn on "slow to mine" blocks just fine. I've not tested this in Single-player just yet, this was only on the BDS server so I can't rule out this being a BDS bug just yet.