Assalamu alaikum
Thank you for this question. It is true what you asked. In this case isha is not late, rather the time of isha is longer than the rest of the prayers. This late night is also the part of isha. But there is a problem. It is only possible if you live away from any mosque. Or otherwise, it is compulsory to join jamat and the reward of jamat is far more greater than even this late night isha.
Wassalam
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