Walker can be an excuse maker/spin doctor for the Cowboys.
There is a difference between playing hardball and just being stupid. Dallas is more the latter. Just refusing to sign player(s) thinking that time will force them to lower their price is idiotic in today's NFL because it largely doesn't work that way. Lamb's asking price isn't coming down the longer you wait. It's going to only go up.
Jerry and his son are just being dumb here UNLESS they are content with the reality that they are OK franchising him for a year and then likely being willing to let him walk in FA in a couple years, which is entirely possible.
They are not going to tag him twice, that's way too expense. So if they are content with the Tony Pollard model, meaning tagged for a year and then left to leave in FA, then it explains their total inaction.