I think it is not a bug but a change that was made in following commit, see:

https://projects.tigase.org/projects/tigase-pubsub/repository/revisions/84a9537deefc05f567f7f633595fb31468eb372d

Changed repository API to accept service jid so each domain can have separate list of nodes.

Updated API to use Packet instead of Element for processing.

As pubsub@domain is diffrent node that pubsub.domain it is valid for both services to have diffrent nodes available. Also PubSub component was modified to support PEP and virtual PubSub service as described in http://xmpp.org/extensions/xep-0060.html#addressing-jidnode and http://xmpp.org/extensions/xep-0163.html and due to that this is rather valid behavior.

OK, I understand reasoning behind using JID as a collection ID and possibility to use it for PEP or providing PubSub functionality on regular user JID but the 'core' problem seems to be mostly related only to two items: pubsub@ and pubsub.. Right now PubSub component advertise the latter, but because of the internal routing of Tigase it also receives requests sent former (even though there is no user registered with that JID, i.e. pubsub@… and I would imagine chances of such are rather slim, but that's beside the point) and we end up with rather confusing behaviour.

As far as Addressing is being considered:

If a pubsub node is addressable, it MUST be addressable either (1) as a JID or (2) as the combination of a JID and a node. [8]

So my assumption that while the change you mention allows (2) we should also still support (1) which, in my understanding only supply address of PubSub service without making the collection distincion based on the actual JID so the scenario is "hey, there is a pubsub component and you can reach it under pubsub@ or pubsub. and it's the same pubsub and it has the same nodes" (I'd say for the sanity purposes we should still differentiate on vhost to keep them separate but that was already present).

As we already discussed this earlier today with Wojciech we only support second form of addressing for PubSub nodes.

Due to the fact that name@domain will be used only for users registred for domain we should not allow to publish/discover nodes at pubsub@domain and force usage of pubsub.domain as this is discoverable address of component. I changed PubSub component to not allow processing of packets addressed to pubsub@domain (name@domain where name is name of component) and to return SERVICE_UNAVAILABLE error.