Eeee... what is so "BU" about this specific block?
The only pool I know signalling BIP109 (2MB blocks) is Slush.
Which is also the first pool that started signalling segwit.
It antpools first block signalling for BU -
https://coin.dance/blocks/unlimited0367f506234d696e656420627920416e74506f6f6c20626a352f4542312f4144362f022058bdab6
efabe6d6d3abbc4fd04647f22af1d514e7fba1c861fd335f4cb9ec0ce5b4a2c67fd8f3c6d040000
00000000006709000019440000
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