Per the website, saver fares earn 30% of the actual points flown.

Just as I checked your message, I checked my Atmos Rewards account and Alaska credited it. They say it can take up to 60 days...so fair enough.
But yeah, back to the topic about Delta - while Delta does not reward miles for the flight itself, if you buy a seat 7 days before the departure (which I am not sure whether it's still possible now that the rules were modified a bit compared to when I purchased the ticket), you'll still get some miles. I earned an extra 107 miles that way, and that's without having any Delta credit cards.

Idk if buying for a bag will gain miles too.

No miles are awarded for luggage fees and is basically limited to seat purchases. DL Comfort Basic fares (which still seem to be only offered in limited markets) earn 2 miles per $1 base. I'm somewhat surprised AA and DL no longer offer at least some miles on Main Basic at a reduced rate as it encourages some loyalty of price conscious customers at minimal cost. No status earning on Basic fares is more understandable as most people buying Basic fares likely don't care about earning status. Now that AA and DL have dropped mileage earning on Main Basic, I wouldn't be suprised if UA follows suit at some point.

Incorrect. 2,500 SM are awarded if you claim that your checked luggage arrived after 20 minutes on a domestic flight.

Not really the same thing as getting miles for paying for checked luggage.

Yep, the reason I used to be a hardcore AA flyer was that AA Main Basic still offered miles back then, apart from the fact that DFW was (and still is) my base. Now that they don't, I switched to Delta and Alaska and I kid you not, I got treated better by both. I am already putting my hands off United since IIRC you need to pay for carry-ons as well, and United does not let you change seats in Basic Economy (IIRC when I bought my ticket, Delta didn't add that verbiage just yet). Both cases do not apply if you fly a partner airline, e.g. ANA on a United ticket.

I'm just glad that I can still pay for a seat on Delta, because on Alaska, your choice of seats that could be paid in advance were premium, first, and preferred seats. I know AA's seats are open for purchase until T-24, not sure about United.

I believe only Delta and Alaska had this promise claim. I wonder how passengers would prove this. Maybe firing their stopwatch on their phones?

I�ve done this at least 30-40 times for 2500 SM with no issues.