I've never had the bushing just slide into place on any bike I've ever owned. The split in the bushing allows the metal to expand just enough that its O.D. is just slightly greater than the I.D. of the hole in the lower fork tube. Its always been a challenge to compress the bushing so that its diameter is small enough to be able to drive it into place. The wine cork solved that problem for me.
I've never tried driving it from above with a seal driver, with the washer in place, because I've never owned a seal driver. I always use the old oil seal on top of the new one, and pound that with a small piece of wood like a 1x4 to drive the new seal into the fork tube. Always worked, so I never made a proper seal driver tool.
I'm guessing that the seal driver tool provides an even force that aligns the bushing into the hole and it compresses as it drives it. So I've been doing it the wrong (hard) way for the last 36 years and didn't even know it. I'll build a 1-1/4 PVC driver and see if it works as easy as you say, that would be great. I actually had thought of that before, but from the looks of it I didn't think the bushing would compress at all just by hitting it from above, so I never tried it. Thanks for the feedback.