Does Apstra reference design support ESI lag with three Leaf nodes?

More than two leaf devices in one ESI segment using ESI-based rack types is not supported. Please see the following docs for details. 

https://www.juniper.net/documentation/us/en/software/apstra6.1/apstra-user-guide/topics/topic-map/junos-evpn.html#junos_evpn_evpn_multi-homing_terminology_and_concepts