[BUG] dune build @check fails mysteriously with overlapping executables

[nojb]

Repro:

$ mkdir test && cd test
$ cat >dune-project <<EOF
> (lang dune 3.0)
> EOF
$ cat >dune <<EOF
> (executable (name main1))
> (executable (name main2))
> EOF
$ touch main1.ml main2.ml
$ dune build @check
File "main2.ml", line 1:
Error: Could not find the .cmi file for interface main2.mli.
File "main1.ml", line 1:
Error: Could not find the .cmi file for interface main1.mli.
$ dune build @all
$

• Do not understand why dune build @check fails but dune build @all passes; and
• Shouldn't this Dune file be rejected by Dune since the two stanzas have overlapping module lists?