If its "temporary," go for it. The washer will probably jiggle and move, which might stretch where the feet are, it will expand/contract a lot because of the varying high moisture content, but I suppose the worst that would happen is you get an air bubble.

This year I used a piece of tarkett fibrefloor for a small 5 x8 bathroom. Not sure how that compares to Marmoleum but it is a loose lay flooring which only has to be secured at the edges. I cut and laid the flooring directly over ceramic tile ( tile has average size grout lines), and used strong 2 sided carpet tape at all the edges. Then the baseboards went back on top of that. It worked great, is completely secured, was eco friendly as it was a left over piece and looks good.

Back in the 1920s, linoleum floor cloths/rugs were very popular. They were placed on wooden floors to “protect” them. I would try it out. Get a remnant for your floor. You don’t really need a big piece. Perhaps one of those patterns that look like encaustic tile? Permit it to “relax,” to flatten it. (Curl will be your enemy.).