A'd like to discuss about threads

Running neo4j server community 4.4.6

I'm running a long query to upload. it is a LOAD CSV query.

I read, from a post of @stefan.armbruster (I cannot find the post) that neo4j is single-thread by design.

I'd like to know if this is still true, because I have some queries that runs in a different ways, and one of them give me these results. where neo4j saturated all the available threads and doesn't respond to the browser.
Indeed, the browser at a certain point disconnects from the server which is no longer able to respond, and closes the connection.

So, please, can someone help me to understand how neo4j uses threads?