Note that so-called “immortal” nodes are often destroyable.
I have written about this topic already:
viewtopic.php?f=47&t=11272
viewtopic.php?f=9&t=11271
The bedrock2 attempts to add indestructible nodes at the bottom of the world, these nodes are almost indestructible, but there are still small but annoying exceptions.
It shouldn't be too hard to rewrite/fork/whatever the bedrock2 mod to build kinda sorta “infinite” walls.