Deparse tries to reproduce code, while Concise shows what's actually there.
A more accurate demonstration:
$ perl -MO=Concise,-exec -e'print if $a'
1 <0> enter
2 <;> nextstate(main 1 -e:1) v:{
3 <#> gvsv[*a] s
4 <|> and(other->5) vK/1
5 <0> pushmark s
6 <#> gvsv[*_] s
7 <@> print vK
8 <@> leave[1 ref] vKP/REFC
-e syntax OK
$ perl -MO=Concise,-exec -e'$a and print'
1 <0> enter
2 <;> nextstate(main 1 -e:1) v:{
3 <#> gvsv[*a] s
4 <|> and(other->5) vK/1
5 <0> pushmark s
6 <#> gvsv[*_] s
7 <@> print vK
8 <@> leave[1 ref] vKP/REFC
-e syntax OK
But the question is about the if statement.
$ perl -MO=Concise,-exec -e'if ($a) { print }'
1 <0> enter
2 <;> nextstate(main 3 -e:1) v:{
3 <#> gvsv[*a] s
4 <|> and(other->5) vK/1
5 <0> pushmark s
6 <#> gvsv[*_] s
7 <@> print vK
8 <@> leave[1 ref] vKP/REFC
-e syntax OK