They can have more than TLV as a stop
If they originate in BOS - -they can add one additional stop (more than 24 hours) on top of TLV.
With the carrier you selected this can really be anywhere in Europe - - and with the award you selected almost anywhere in the middle east.
For instance...they could fly BOS - FRA in F -- then fly to say Warsaw...and then on to TLV and back to BOS through FRA...they just need to keep it all on the Star Alliance. (again -- something like BOS - FRA - ZRH - TLV - FRA - BOS).....there are a lot of choices!
If they want to get really creative -- they can also do an open jaw with TLV as one end and just buy a ticket to the other end of the jaw.