That they don't offer peering for free but charge for it. The idea of peering is that both sides gain from it as they reduce the traffic routed through middlemen like level3. So you both go to internet exchanges like DE-CIX, and pay a basic fee that you may participate in the exchange but you get all the connectivity to other ISPs from that exchange. But some ISPs don't do that and require you to peer in one of their own datacenters, requiring you to pay them money. You are now their customer instead of a partner. A big German partially government owned ISP did this for a while until they finally gave up a few years ago.

HE doesn't charge for peering though. The complaint was that HE was leaking peer routes to other peers per default, which is normally only done if you are a customer (which can be nice if you want this, but can lead to sub-optimal routing if you don't want this).