No we didn’t in practice - because you also need the return routability.
Modern day example: If you are connected over WiFi and 3G over two different ISPs, the packet for your (probably RFC1918, statefully NATted by your home gateway) address of the WiFi interface has absolutely zero chance of arriving over 3G (which probably has a different RFC1918 address, statefully NATted in the CGN in the mobile infra). And vice versa. So strong host model vs weak host model is irrelevant in this context.
MPTCP works absolutely fine in this scenario.
MIPv6 reportedly works to roam (assuming no NAT66 in the path), but can not use two paths at once.
Modern day example: If you are connected over WiFi and 3G over two different ISPs, the packet for your (probably RFC1918, statefully NATted by your home gateway) address of the WiFi interface has absolutely zero chance of arriving over 3G (which probably has a different RFC1918 address, statefully NATted in the CGN in the mobile infra). And vice versa. So strong host model vs weak host model is irrelevant in this context.
MPTCP works absolutely fine in this scenario.
MIPv6 reportedly works to roam (assuming no NAT66 in the path), but can not use two paths at once.