That's a great question, we will have to dig into that further, but I’m suspecting the the same as you. Another source of these might be exchanges and wallets, for example when kraken  initially launched their node. 

lncapital

I'm surprised 6% of currently opened channels are from batched channel openings. Do you know what type of nodes are the ones doing the batching? IE, are there single parties that are the most significant in those or is it dispersed across many nodes?

I believe any channels bought through Pool would show up as batched if there are multiple channels purchased in a single round, I wonder how many come from that itself.