Here, ***tous*** is an adjective agreeing with the pronoun ***ceux*** so according to the rule you linked to is pronounced **/tu/**.

Had it been pronounced **/tus/**, that would have lead to **/tus.sø/**.

Compare:
> *Je veux les miens **plus ceux** de mon frère* (I want mines and my brother's ones)

where *plus ceux* is pronounced **/plys.sø/** and:

> *Je ne vois **plus ceux** de mon frère* (I don't see anymore my brother's ones)

where *plus ceux* is pronounced **/ply.sø/**.