Sorry, but you are wrong. Since immemorial times and K&R release 1,

if(a) if(b) c(); else d();
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is DEFINED as

if(a) { if(b) c(); else d(); }
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But, this does not mean there is no ambiguity. It's just plain wrong to assume things without the braces because software changes constantly. So, one day you have

if( a )
  if( b )
    c();
  else
    d();
else
  e();
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and then you see some reason for the else d(); to go away, and you stay with

if( a )
  if( b )
    c();
else
  e();
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That does not do what you intended and you can be looking for this bug in another place kilometers/miles away (in the code) because you left out some initialization done by e(); etc etc.

IOW: You could do that -- because it's really well-defined behaviour for the C language --, but it does not mean you should.