Basic q regarding STP initial convergence

Hi all
In several texts I've read that switches upon convergence each think they
are the root bridge AND send config pdus out all ports.
However in Cisco's implementation, with the intial blocking state being 20
secs, and having the ability to only receive config pdus from neighboring
switches,
while each switch upon initial convergence may THINK they are the root
bridge is it true that in general they do not have a chance to advertise
that as a result of possibly receiving a better bpdu from a neighboring
switch?

Plus, was the initial 20 sec blocking state proposed by Cisco to actually
allow switches enough time to learn the identity of the root bridge before
sending bpdus of their own?

Please advise.

-- 
Regards
Roy
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