Yes, you are wrongly interpreting the documentation. The selection for the best gateway is for downlink only. As I mentioned all uplinks received at the backend within 200ms will processed and used for deduplication at which time all relevant metadata (gateway information, RSSI, SNR etc) will be combined and after that the entire set of information will be delivered to the application. There is no best gateway for uplinks, all gateways that received the message without errors (CRC and message integrity check) are equally good.
Only for downlinks a best gateway will be chosen from the list of gateways that received the uplink and to determine that gateway RSSI, SNR and available airtime are used.
The second ‘error’ is referring to the outdated V2 documentation, go to https://www.thethingsnetwork.org/docs/devices-and-gateways/#gateways for current documentation. The sentence is worded a bit differently which might be less confusing.