SkyLight under blocks not fixed

In 1.14.2, on my server, I made a moutain, but skylight was at 14 under the moutain. I saw that bug is fixed in 1.14.3, so I try in 1.14.3, but it did not work, skylight was not at 0 again. So I placed a platform above the montain... the problem is the same, then, I placed a platform inside the montain but there is skylight again. Can you fix this please?