Why is Derek smiling at Mike in the van?

In the scene when the crew drives back to the gate Derek weirdly smiles at Mike and Mike is like „huh? You smiling at me? Ok…?“ and Derek is totally weird looking like dazed.

What was that? Why did they decide to keep that in the Final Cut?

Was he just happy? Gay glimpsing at Mike? Or did he think Maik is smiling at him because Jane/Eleven is not actually there but a projection for Mike?