The big novel feature in Nakamoto consensus (the Bitcoin paper one) is precisely that it gives you Sybil-proof BFT without a CA. That's the whole reason for the massive energy consumption.
I'm fine with a sybil resistance mechanism (although it's not sybil-proof, and some particular forms of sybil-resistance are based on faulty models [1])
The problem is that this paper doesn't employ such mechanisms:
> This assumption is problematic for P2P systems...they must either exercise centralised control over which nodes are allowed to join the network, or employ expensive Sybil countermeasures such as proof-of-work [30]. This paper shows... is possible to guarantee the standard CRDT consistency properties even in systems in which arbitrarily many nodes are Byzantine, e.g. where the Byzantine nodes outnumber the correct nodes. This makes the algorithms immune to Sybil attacks...
This argument is incorrect. The counter-example is Dolev-Strong [2]. The number of faulty nodes is not fixed, but still needs a CA.