What you linked is interface bonding. That's the easy way to do it when you have multiple physical interfaces on the same network. What you have to do in a case of aggregating multiple connections locally is equal-cost-multipath routing that round-robins your requests across multiple interfaces.
This isn't too useful for ordinary browsing, but it is useful for things like torrenting because that opens many connections to many different servers, so relatively decent load balancing is achieved.
This feature, too, has been in Linux kernel for well over a decade.