Slide 22 is a bit confusing. The error rates on that slide are usually better described as positive and negative test results. Before talking about false positives (FP), true negatives (TN), etc. let us consider what the test actually is. The McNemar test is a test for difference of proportions. The Wikipedia entry for the McNemar test relates that for
| Test 2 positive | Test 2 negative | Row total
Test 1 positive | a | b | a + b
| | |
Test 1 negative | c | d | c + d
Column total | a + c | b + d | n
The null hypothesis, $H_0$, of marginal homogeneity states that the two marginal probabilities for each outcome are the same, i.e., $p_a+ p_b=p_a+ p_c$ and $p_c+ p_d=p_b+ p_d$.
Thus the null and alternative hypotheses are
H_0 & :~p_b=p_c \\
H_1 & :~p_b \ne p_c
Thus, the alternative hypothesis means that $p_b$ ≠ $p_c$; the marginal proportions are significantly different from each other. To adapt this for TP, TN, etc. see similar answer at https://stats.stackexchange.com/a/241844/99274. This requires that one test is a "truth value" which is not necessarily native to the McNemar test, which test actually only requires that we have two tests, not that one of them is a "standard."