Yes and no. GPS has 10 bits for the week number (so 1024 weeks)
This code is using the number of leap seconds that have happened to sanity group of 1024 weeks we are in. The assumption is that by December of 2022, we would have another leap second, so if we had fewer than 19 total leap seconds, then something has gone wrong. However due to incorrect arithmetic, this sanity check is looking at October 2021.
Further comments point out that the sanity check need not be in production code at all, but should be moved to test code.
GPS also has a field indicating when the previous or next leap second was or will be; this field is 8 bits or about 5 years. The last leap second was in 2016 and no future leap second has been announced. So GPS needs to mark a non-leap to keep the week offset in bounds.
This happened before in 2003 during the previous long gap in leap seconds (1998-2005).
This code is using the number of leap seconds that have happened to sanity group of 1024 weeks we are in. The assumption is that by December of 2022, we would have another leap second, so if we had fewer than 19 total leap seconds, then something has gone wrong. However due to incorrect arithmetic, this sanity check is looking at October 2021.
Further comments point out that the sanity check need not be in production code at all, but should be moved to test code.