Segwit didn't exist when CK implemented solo mining in cgminer those times and as explained before cgminer was put in archive mode by CK.
Retrospectively complaining CK didn't implement something that came later or insist calling it "bug" is moronic. Kano still deliberately avoids unlocking solo functionality in his current versions, and he tries to justify this in the sense that it would be foolish to mine on a dedicated full-node. Of course, it should be clear to everyone that a full node and mining on such a full node requires certain minimum requirements and how important performance is in the context of the mining process. A possibly found valid block must finally find its way into the blockchain in the shortest and fastest way and reach many nodes at ultra-fast speed, otherwise one runs the risk of stale shares and orphan blocks. Not only a high-performance full node is important, but also the speed to the Internet plays a role, as well as the routers and hops in between. At best, everything runs in a data center with high-quality devices and top performance with an extremely fast Internet connection. Keep in mind the sheer amount of data (some TBs per month) just for the GBT traffic so running this at a data center makes only sense if your miner is located on-site, too. This information could all be mentioned, explained and ultimately left to the user's free decision to solo-mine on a full-node.