I haven't used netboot ever, so can't really advise on that 100%, but looks like it's more of a 'recovery options' and in any case b'cos your intention is to wipe and install a new OS, so I suggest you try these steps and let us know if it helps your case.
1) Download 9.5 (Stable release) and put it in your web(http) server. 2) Choose option 7 – install new software first, and enter the URL of the 9.5 image from your webserver. 3) Once 9.5 is installed on the internal boot device, boot into maintenance mode from the boot menu and unassign all drives from each node. 4) Reboot each node, and then choose option 4 – wipeconfig. Once the wipe is finished, the system will use ADP on the internal drives and be ready to setup unless you don't want ADP and want to use whole disk partition.