No Chemist, I mean the tongue stays down even when making these sounds. Only the front part of the tongue moves up and touches the ridge, well, you can call it the middle part if you want, but the tip keeps touching the lower teeth all the way.You mean the tongue is lying down by default but moves up to the alveolar ridge to make the sounds right?
The upper position is used to make Ч, Щ, Л sounds (although I can also make these with the tip down), and I'll get the right sounds but it's more convenient to move the tip up for these sounds.