Aria FAQ says: "Multiple concurrent inserters into the same table."

However, if I create a table with autoincrement PK, ENGINE=Aria ROW_FORMAT=PAGE (tried also TRANSACTIONAL=1)

then there is no concurrency - only 1 thread is working, others are stuck in "Waiting for table level lock". 

I couldn't find the exact description of Aria engine behaviour in docs/faq/discussions - is it the way it's supposed to be?

Thank you!