That's not what the numbers tell us (again 3b33a14380 vs 7922131bb2):
make -j1 check: 181s (69s byte-compilation, 112s execution) vs 162s (58s
byte-compilation, 104s execution)
make -j4 check: 45s (17s byte-compilation, 28s execution) vs 40s (15s
byte-compilation, 25s execution)
make -j8 check: 26s (9s byte-compilation, 17s execution) vs 23s (7s
byte-compilation, 16s execution)
In short, the compilation time in make check is slower (which is
expected), but the execution time in make check is also consistently
~7% slower.