I actually did know that, but it wouldn't mean anything to most people, and the actual time frame attached to the present perfect tense depends a lot on context. If you say, "I have done things I'm not proud of," that implies a vastly different time period than "I have hated him since he walked out on me." So I thought it was simplest just to point out that it was not the past tense and that it reads most naturally as something that has been true up to the present.