台 which meant and sounded the same as 貽 (malt candy), 台 which meant and soumded the same as 胎, and 臺 which meant watch tower sounded almost the same in Old Chinese, and they were attested around the same period. So it doesn’t make sense to say 台 is a simplified version for 臺, especially not for transcribing Taiwan, since it’sa phonetic translation of the Sirayan word Tavoan.