In our picture here, the red dots are the central group of experts, the white dots are the knowledge users or knowledge workers, and the white arrows are the flow of knowledge.
In the centre-out model, the knowledge is created by the experts in the centre, and "pushed out" to the knowledge workers, in the form of doctrine, work instructions and policies. The centre owns the knowledge - they are the Knowers - while the knowledge workers apply the knowledge - they are the Doers.
In the out-and-in model the knowledge is managed by the experts in the centre. Knowledge is gathered from the knowledge workers, synthesised and validated in the centre, and transferred back out to the workers. There are feedback loops such as lesson learning systems which mean that the central knowledge is always tested against reality and updated regularly. The centre stewards the knowledge and validates it, while the knowledge workers both apply and improve the knowledge.
In the multiflow model, the knowledge flows between expert and worker, worker and worker, worker and expert. Knowledge is created, updated and validated by all parts of the system, and is available realtime. The knowledge is managed and owned by the Community of Practice, while the centre manages and stewards, not so much the knowledge itself, but the knowledge-creating and knowledge-validating system.
The first model seems very old fashioned nowadays, and the third model seems much more attractive, and is becoming more common (see for example the use of Wikis to develop Army doctrine).
However in reality all three models may be needed simultaneously in any one organisation, to deal with different types or different levels of knowledge.
There may be mandatory knowledge, such as knowledge of company law, or knowledge of policies such as anti-money-laundering or anti-corruption policies, which has to be mandated and controlled from the centre.
There may be strategic knowledge, driven by company strategy, which can certainly be tested in the business, with clear (and welcome!) feedback, but which needs to be owned and coordinated centrally and strategically.
There may be operational and tactical knowledge which is owned by the Communities of Practice, and handled within wikis and blogs and discussion forums (and indeed the Army wikis mentioned above were specifically for tactical knowledge).
So it is not as simple as saying "model 1 is old fashioned and rigid and Bad, model 3 is free and liberated and modern and cool and Good".
It is, as is so often the case in Knowledge Management, a case of determining which model is most appropriate for which knowledge.