Also note that DL flights to/from Alaska fit into the 6 hr rule, not the 4, for domestic. Even then during the slowest part of the winter it’s not uncommon for some DL flights to have greater than 6 hour connections to/from AK. So, while DL tries its hardest to impose the 4/6 rule, it’s not 100%.

Also note that even on international connections greater than 6 hours, DL systems will default to short checking a bag, but a good agent can override.