Synology’s implementation of btrfs over md with lvm extension “as is” — definitely. I would not use it for anything else either, much less storage node. It has drawbacks of both conventional raid and complexity of btrfs:
As you mentioned in one of the threads there, (Node randomly restarting. Possibly high memory usage - #21 by Alexey) btrfs configurations other than mirror “are not considered stable”, for the past decade, whatever that means. Synology however I did not “fix” anything: They avoided the problem by using conventional raid instead. So you have regular raid, and then you have btrfs laid down on top, and you have volume manager extension for repairing rot. That last bit is what they innovated with in dsm version 6.2.
I skimmed through those threads now and read a few of them before, and I don’t think I saw attempts to tune the filesystem: such as disabling checksumming, turning off access time updates, etc.: you can get comparable to ext4 or better performance from btrfs, just not on Synology: they put marketing first by picking “huge list of features at low cost” approach, and their users pay with loss of performance for their design choices.
And separately, I agree their TiVo approach to using opensource is a bit disgusting. They do release the changes back: but those changes are no more than hooks into their opaque shim layers, and on old and buggy version of software. I had to look trying to fix multiple issues they acknowledged but never actually fixed. (Yes, I strongly dislike Synology. I went from oh, cool NAS OS and hardware to profanities every time I had to interact with the boxes in a span of two years)
So I would rephrase your advice to “avoid using non-mirror btrfs configs on Synology for hosting storage node, especially on low end hardware, and without a lot of tuning”. BTRFs itself is a fine FS.