IEEE 802.11s is an internationally approved standard. IEEE is a Standards Developing Organization (SDO). Wi-Fi Alliance is not an SDO. The EasyMesh specification does not qualify as standard.
IEEE 802.11s defines a self-organizing, layer-2 multi-hop network. IEEE 802.11s seamlessly integrates with any other IEEE 802 network. It works transparently. Thus, it supports spanning-tree and other L2 messages. With IEEE 802.11s, mesh stations may connect with one or more other mesh stations.
In contrast, EasyMesh always forms a tree structure. There is a root AP. Other APs connect to the root. In upstream direction (towards the root), devices behave as clients. In downstream direction, devices act as APs. Thus, EasyMesh is able using the traditional WPA2 encryption scheme. IEEE 802.11s, however, does not specify such hierarchy. All nodes are on the same level. Hence, IEEE 802.11s cannot use the hierarchical WPA encryption method. Instead, IEEE 802.11s relies on Simultaneous Authentication of Equals (SAE) that permits either end of a link to initiate a key exchange. In contrast, WPA2 always relies on the hierarchy of authenticator and supplicant.
Conceptually, IEEE 802.11s is much more advanced and modern than EasyMesh. However, it's not widely supported by the industry. EasyMesh, in contrast, is a quick and dirty hack. However, EasyMesh also supports non-mesh aspects (e.g. ISPs may use it peek into their customer's deployment to help them optimize their Wi-Fi).
There are many more differences. In summary: 802.11s is in the Linux kernel, also Google uses it. However, all in all, there is little support for it. In contrast, there are many more commercial products that support EasyMesh. However, EasyMesh is far from being a success. It does come way too late and most Wi-Fi mesh solutions use proprietary solutions that are non-interoperable.