Some more data points:
- In February, I booked ARN-MUC-LIS, LIS-ZRH-ARN via Lufthansa. The LH6970 MUC-LIS leg operated by TAP was in Economy (V). This resulted in 1300 SAS EuroBonus points!!
- In May, I booked TAP flights ARN-LIS-OPO via Expedia and got Economy (E), which was denied by SAS ("Your ticket with Tap Portugal was booked in E class and tickets issued in this booking class do not qualify for EuroBonus points.") Oddly, the boarding pass says Class Y.
- In early June, I booked TAP "BASIC" flights (again ARN-LIS-OPO) on flytap.com and got Economy (O) (O22BSC0A) outbound, Economy (E) (E22BSC0A) inbound. As per SAS rules, this also resulted in no earnings. (Again, the boarding passes say Class Y.)
- Later in June, I booked OPO-ZRH-ARN via Swiss, including two TAP flights (OPO-ZRH and ZRH-OPO). This resulted in Economy (L) outbound, Economy (V) inbound. For the L, I got 225 SAS EuroBonus points; for the V, I got 1000 SAS EuroBonus points. (Again, the boarding pass says Class Y.)
- In early October, I booked TAP "CLASSIC" ZRH-OPO on flytap.com and got K23CLC0B. This resulted in a measly 250 SAS EuroBonus points. (Again, the boarding pass says Class Y.)
- I just booked a TAP "CLASSIC" LIS-ARN and "BASIC" ARN-LIS directly on flytap.com. I got E22CLC0A and E22BSC0A, so I am not expecting anything
… From the above, I can only conclude that, for best earnings, book via a partner airline, not directly on flytap.com! (which my computer insists on auto-correcting to flytrap…)