New form of 51% attack via lightning's revocation system possible?

The lightning network, which was created to provide faster and cheaper transactions on the Bitcoin network, may be vulnerable to a new form of 51% attack that allows an attacker to steal an arbitrary amount of funds. According to Rene Pickhardt, who is studying the revocation system of duplex micropayment channels in detail, this type of attack can be executed by secretly mining enough blocks after fraudulently spending old commitment transactions and no one seeing it during the to_self_delay period. The attacker could steal up to 99% of all the bitcoins allocated in the sum of all payment channels the attacker was connected to, making it more harmful than a successful 51% attack on the bitcoin network. Pickhardt warns that he does not see any reasonable way of preventing this form of a 51% attack other than creating payment channels that do not offer the possibility of revocation.