I saw someone with a similar tailgate pad load his e-bike at a trailhead parking lot . He lowered the tailgate, put the bike in the bed and raised the tailgate under the bike. It was awkward at best and would only work with a single bike.
I also carry my bikes in a pickup and long ago gave up lifting them into the bed. At 74, these heavy e-bikes are a chore for me to transport. IMO, If you're going to dedicate your pickup bed to carrying bikes, why not buy or make something like this:
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These have been posted here many times and the first one is my avatar pic. I've been using variations of this rack for over 10 years and the concept works very well.
It's made from scrap pieces of PVC pipe and cost less than most hitch style racks. There is no attachment to the truck at all and the rack easily slides out when not in use.