While I agree with your premise that Walker isn't a huge risk to lose on waivers, he wasn't passed over by every team the second time he was waived. The Caps had 1st waiver priority because he was claimed from them that year.
They only get first crack if he is waived twice, Caps were 25th in the order.
This time around, the Caps are 25th in the waiver order if they want to bring Walker back. If no other NHL team puts in a claim, the Caps could re-claim Walker and assign him to Hershey – their plan all along.
Edmonton Oilers place Nathan Walker on waivers