yes, if you use the stack loader. The normal loaders do not support stacking (same as normal inserters do not). The top image on https://mods.factorio.com/mod/miniloader-redux shows the stack loader (the image shows the chute, four regular tiers (normal, fast, express, turbo for SpaceAge) and the stack loader.
It is possible to create custom tiers that also stack. I am open to PRs but in the "vanilla" set of loaders, only the stack loader does.
