`...` is just short for qx`...`, which is short for readpipe(qq`...`).

$ perl -MO=Concise,-exec -e'`...`'
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <$> const[PV "..."] s
4  <1> backtick[t1] vK
5  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'qx`...`'
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <$> const[PV "..."] s
4  <1> backtick[t1] vK
5  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'readpipe(qq`...`)'
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <$> const[PV "..."] s
4  <1> backtick[t2] vK/1
5  <@> leave[1 ref] vKP/REFC
-e syntax OK
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This is by no means new; this has been the case for at least 18 years. (The oldest documentation I could find is perl5.005_53 from Oct 31st, 1998.)