The difference between the first and second halves had as much to do with Licha choosing whether or not to try key passes as it did with Amad and Garnacho coming on. Hojlund and Mainoo were both making runs like crazy for the first half hour and every time you could literally watch Licha see them and decide against it. Normally he goes for it.
I don't blame him, I think it was a direct instruction from Amorim. Clearly the strategy was control the first half, minimal risk-taking, and push for the win in the second. And it worked, even if it did make the first half completely dull.