While I've not read their concerns in-depth, I think it makes sense. SARS-CoV-2 is highly effective at infecting cells with the ACE2 receptor, including blood vessel cells. Excessive binding and activate of ACE2 also throws off the balance in the renin-angiotensin system (RAS) that regulates vascular functions. The spike protein of SARS-CoV-2 probably makes this worse.

But at least I'm not concerned about this happening with the vaccines since they use spike proteins with proline modification, which prevents the vaccine-derived spike proteins from binding to the ACE2 receptor.