For some time (probably quite a while and possibly a long time) the reconnect mechanism involving a "cookie" has not been working correctly for TCP-connected agents (JNLP). Perhaps it never worked correctly for all or some of the protocols.
The impact is quite negligible, as by itself this mechanism accomplishes little. Pretty much all it does, would still need to be protected by other mechanisms. As one piece of robustness and retries, it provides some value. Getting it working again could provide some benefit, particularly in clearing up confusing for people reading logs.