Is a pattern rule implicitly double-colon?

[Fangrui Song]

% cat Makefile
.SUFFIXES:
%.o: %.c
        touch $@
%.o: %.d
        touch $@


% rm -f a.o b.o; touch a.c b.d; make a.o b.o
removed 'a.o'
removed 'b.o'
touch a.o
touch b.o


The behavior is similar to double-colon rules. It can not be explained
by

> If more than one rule gives a recipe for the same file, make uses the
> last one given and prints an error message.

in 
https://www.gnu.org/software/make/manual/html_node/Multiple-Rules.html#Multiple-Rules


Context: I intend to use such multiple rules for one %.o target in an
lldb Makefile https://reviews.llvm.org/D94890