Whenever the SPF computation determined there is more than one primary next-hop for a prefix, it will not program any LFA next-hop in RTM. Thus, the LDP FEC will resolve to the multiple primary next-hops in this case which provides the required protection.
Also note that when the system ECMP value is set to ecmp=1 or to no ecmp, which translates to the same and is the default value, SPF will be able to use the overflow ECMP links as LFA next hops in these two cases.