rom flashing – Why is my phone missing “product” partition contained in lineageos distribution?

I have a OnePlus 7T, and am trying to install lineageos on it. The adb sideload method failed, and a forum comment led me to look into doing a manual installation using fastboot as described in wiki.lineageos.org/devices/hotdogb/fw_update.

After extracting the images from the lineageos hotdogb distribution using payload-dumper-go, and also extracting the images from oxygen updater package for OnePlus 7T for comparison purposes, it appears that each image should correspond to a flash partition on the phone.

When I attempt to fastboot flash the partitions from the lineageos distribution, this completes successfully for most of these partitions, except “product.img”, for which fastboot fails with the message

"remote: 'Partition not found'"

This happened for a couple other images as well (recovery, system_ext, vbmeta_system). Similarly I found that the Oxygen distribution I mentioned earlier contains an image “opproduct”, which gives the same message.

From adb if I run

ls /dev/block/by-name

I can see that the flash attempts that succeeded do have a partition listed here, but the ones that failed don’t. How are these partitions created? Can I add the missing ones for the lineageos distro .img files myself somehow?