This is false. There are several developers working on knots. @Super Testnet proved this out a while back.

It seems to have about 12 active developers who deliberately contribute to it That is a lot different from having 1 such developer, but it's still not enough to be safe imo It is also good that much of the code is the same as what's in Core, it means a lot of the review effort put into Core helps Knots too