Yes its almost to good to be but it IS. I applied for ssdi and was awarded in 1992 but I did not know I could get some ssi for the time I was not earning . Not necessarily. Only for post-SSI application months where you have very limited resources and no income, not even SSD retro income.
I believed That the person either took ssdi because they had enough quarters or they took ssi because they did not have the quarters. Hmm, unfortunate you didn't discuss with a lawyer then. Of course, in 1992, there were not very many of us that engaged in this kind of work.
I got 18 months of past ssdi benefits . Seems I could have gotten 18 months of SSI benefits too. If your SSDI was greater than the SSI max amount, in any of those months, it would have put you over the income limit and you wouldn't be eligible for SSI for those months. Remember, SSI is welfare and only for those that don't really have income to speak of for those particular months.
What you don"t know can cost you. Yes. In my case another 9 thousand at 500 a month Probably not - certainly not if you got SSDIB for those months. Unearned income such as SSDIB, in a month (retroactively), will count dollar for dollar against potential SSI benefit after the first $20. You can do that math and determine if your SSDIB would have kicked out your SSI.