I'm trying to understand whether a long CTD basis position needs to incorporate slide/roll when computing basis net of carry (BNOC).
I am told the answer is no but I am not sure why. I am well aware of carry as an important consideration in the context of BNOC and one needs to subtract out the pure carry on the CTD, i.e. the coupon income - financing/repo cost to gauge relative value in futures. However, why wouldn't slide/roll also be netted out in the calculation? If you're long the basis and you own the CTD then that bond will generate some rolldown yield or slide on a daily basis (equal to the 1/number of business days until delivery * total roll to delivery date).
Some guesses I have are that the assumption of static yield curve for roll is too limiting and/or long basis traders typically lend out the CTD in repo and in that case they wouldn't earn slide but I don't think this is the answer. Any thoughts?