In my opinion, he has improved. Those 2 fights were almost 4 years ago! He was just turning 24. A lot of improvement and experience happens in the mid-20s. He isn't a kid anymore. Nate has always been talented, but we have never seen him completely dominate 3 guys in a row like he just did.
Bendo can certainly win that way if he is good enough to avoid the subs. But Nate is better standing and on the ground. While it may be Bendo's best option, rolling around on the ground with Nate is never a safe route for anyone.
Bendo has 5 rounds to lay. And if he does, at least everyone will know who the real fighter is afterwards. If he takes him down and decides not to lay but be aggressive, he will get sub'd.
I think the difference is Nate's striking. He was always pretty good, but wrestlers could get inside and ragdoll him quite easily. Now that his striking is on par with Nick's, people are easily caught on the back foot. Even a big guy like Bendo will struggle to take the centre of the ring, and Diaz will be pushing him back. It's very hard to get past steller striking to get into the wrestling zone. Also his Jiu Jitsu has seemed a little bit better aswell. The submissions over Jim and Gomi were very good, and although he's always been a great submission fighter, he's really brought himself up to elite championship level all round.
I actually only really watched Nick at first. My first proper Nate fight was the Gomi one, and I was thinking "Why is this guy not at the top?". He continued dominating great fighters like Miller and more impressivly Cerrone, and it was only then that I looked back to see how much he has improved.