Aria2 is updated, therefore it does not act as before. See the usage, and you will get:
As of 1.10.0 release, aria2 uses 1 connection per host by default and has 20MiB segment size restriction. So whatever value you specify using -s option, it uses 1 connection per host. Please note that this connection restriction is applied to 1 host. If you specify multiple hosts, aria2 will use them all and open multiple connections. To make it behave like 1.9.x, use -x16 -k1M. See --max-connection-per-server and --min-split-size in the manual page.