Is it expected that tests/sys/kqueue/libkqueue/Makefile and tests/oclo/Makefile should use PLAIN_TESTS_C= instead of using += ?

I see:

/usr/main-src/tests/sys/kqueue/libkqueue/Makefile:PLAIN_TESTS_C=
kqueue_test

/usr/main-src/tests/oclo/Makefile:PLAIN_TESTS_C=        oclo oclo_errors
ocloexec_verify

But the rest use += :

# grep -r 'PLAIN_TESTS_C.*=' /usr/main-src/tests/
/usr/main-src/tests/sys/aio/Makefile:PLAIN_TESTS_C+=	aio_kqueue_test
/usr/main-src/tests/sys/aio/Makefile:PLAIN_TESTS_C+=	lio_kqueue_test
/usr/main-src/tests/sys/kqueue/libkqueue/Makefile:PLAIN_TESTS_C=	kqueue_test
/usr/main-src/tests/sys/netmap/Makefile:PLAIN_TESTS_C+=	ctrl-api-test
/usr/main-src/tests/sys/file/Makefile:PLAIN_TESTS_C+=	ftruncate_test
/usr/main-src/tests/sys/file/Makefile:PLAIN_TESTS_C+=
newfileops_on_fork_test
/usr/main-src/tests/sys/kern/Makefile:PLAIN_TESTS_C+=	subr_unit_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+= big_pipe_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+=
pipe_fstat_bug_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+= pipe_ino_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+=
pipe_overcommit1_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+=
pipe_overcommit2_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+=
pipe_reverse2_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+= pipe_reverse_test
/usr/main-src/tests/sys/kern/pipe/Makefile:PLAIN_TESTS_C+=
pipe_wraparound_test
/usr/main-src/tests/sys/kern/tty/Makefile:PLAIN_TESTS_C+=		tiocnotty
/usr/main-src/tests/sys/fifo/Makefile:PLAIN_TESTS_C+=	fifo_create
/usr/main-src/tests/sys/fifo/Makefile:PLAIN_TESTS_C+=	fifo_io
/usr/main-src/tests/sys/fifo/Makefile:PLAIN_TESTS_C+=	fifo_misc
/usr/main-src/tests/sys/fifo/Makefile:PLAIN_TESTS_C+=	fifo_open
/usr/main-src/tests/oclo/Makefile:PLAIN_TESTS_C=	oclo oclo_errors
ocloexec_verify


(Not that the above contributes to my problem, but I noticed this while
trying to figure out why my armv7 builds fail but my aarch64 builds
work. The difference being armv7 is not even trying to build
tests/sys/kern/tty/tiocnotty but its install is trying to install it.
aarch64 both builds it and installs it.)

-- 
===
Mark Millard
marklmi at yahoo.com