I'm looking at plans on the coveredCA site, and I see both terms used. However, my understanding is that coinsurance only kicks in after the deductible has been paid anyways, so "coinsurance after deductible" seems redundant both in and of itself and with just the term "coinsurance."
"coinsurance after deductible" seems redundant
You're right, it's redundant.
If a plan has a deductible, the deductible applies unless it is waived. A deducible is the amount of money the insured pays before the carrier will pay. The comparison you are looking at is simply reversing the waive logic. Rather than indicating where the deductible is waived, it is indicating where the deductible applies. You might notice that 3 of the 4 benefits listed are "after deductible" meaning the deductible has been waived for one of them.
"Coinsurance after deductible" is redundant because everything is after deductible unless the deductible is waived.
"Coinsurance" means the amount you have to pay on any claim.
When they say "20% coinsurance after deductible", this means that you have to pay the entire amount of all bills that this clause applies to until you reach the deductible, and after that you pay 20% and the insurance company pays 80%. "100% coinsurance" means that the deductible is irrelevant, you always pay 100%.
I suppose it's redundant in the sense that if they said "100% coinsurance after deductible", that would mean you pay 100% until you reach the deductible, and after that you pay ... 100%.