I don't think the result would look anything like this. All that graph is doing transposing the results under the current UK system to the German methodology.

If the UK were to implement the German system I expect the results to look rather different. A lot of the smaller parties (Greens, UKIP/Reform/whatevertheyrecalledthesedays) will have a much bigger share while the bigger parties will lose votes.

Simple reason being that many people at the moment will vote for the "lesser evil" (eg maybe Labour even though they would prefer Green) simply to avoid their vote being a "lost vote" and to keep the "large evil" (in this example the Tories) out. If they were to vote for a small party there's a possibility the "lesser evil" will lose against the "large evil", so they do some tactical voting.

With proportional representation tactical voting in this manner isn't really that necessary any more, so the smaller parties will likely gain significant votes.