There's one Big thing here, They recorded 7 positive tests and 13 isolations due to being tested on Monday following several days of not being tested. The ACC (and thus I assume ND) is only testing 3 times a week. Twice using PCR (Molecular) tests and once a week using an Antigen test. (this is according to a recent SI article but the ACC's own data shows these testing types may be the opposite). This leaves a chance of the facilities and practice field can become a spread area as well as contact tracing between players on off days. This means there is a lot of opportunity for widespread contamination in a short time across the entire team.
The Big Ten is doing daily antigen testing along with a weekly PCR test. If you come up positive with an antigen test you aren't allowed near the facility and are also immediately given a PCR test regardless of when your last one was.
They also are keeping players separated as much as possible outside of the facilities as well. (basically distancing from anyone on the team you don't live with outside of the testing window.)
Also, both the Antigen and the PCR test kits the Big Ten is using are far quicker than the current tests and the Antigen test kits the Big Ten is going to use are also said to give far less false negatives than the ones currently in use making testing far quicker and more accurate than what is currently being done. As far as has been shown only the Big Ten and Pac 12 are using 2nd Gen Covid Test Machines, the others have been using 1st Gen Machines and/or have been using off site labs for their test results.
IE: The Antigen testing that has been done by the ACC thus far takes 15 minutes to up to an hour to get a result and has false positive rates from as high as 88% to as low as 70% depending on the source. The Antigen test machine that Nebraska is using, processes the test in 3 minutes and claims to have a 96.7% accuracy rate.
Also the ACC's current PCR testing apparently takes 2-3 days to get a result back. Nebraska ( and the Rest of the Big Ten, I believe) gets their PCR test results in 6-8 hours.
All this leads to FAR fewer false positives, a virtually nonexistent chance of the teams facilities or practices being a contaminated zone and a MUCH lower number of contact trace instances of quarantine across the team for the Big Ten as opposed to what the SEC, Big 12 and ACC are currently doing. It's not 100% effective but it's also far less likely we see large enough outbreak numbers across the teams to reach the 5% danger threshold compared to some of these other teams who are having to quarantine entire player position groups due to contact during meetings or off facility gatherings.