Good point, why is the oil band there on a solid flat tappet that has no push rod oiling? Do manufactures use the same tappet body for both solid and hydraulic tappets?
Most solid Chrysler lifters are not just a hunk of solid metal. They have a plunger, too, just not a hydraulic plunger, but an oil metering plunger and they need to be lubricated as well. Their plunger is not spring loaded and regulates the flow of oil. You can tell an oil metering lifter by shaking it and hearing the plunger rattle. Since they're not spring loaded, the plunger moves freely. The oil metering solid lifters are actually the preferred lifters for solid flat tappets, IMO.