Ive rebuilt a few engines over the years and was under the belief that lifters should be filled with oil when fitting.
That was before a good mate and GM trained mechanic told me not to and the only a light oil was used when assembling the lifters and asembly lube applied to all components to protect on startup.
So yes in my opinion the soft inital compression is just an empty lifter.
Also filling new lifters with oil causes the valves to stay open , making startup dificult.leading to excesive cranking and oil starvation.
Cheers Nath