Not quite. An unrealized plan can be well-developed, but fail at the last minute. An embryonic plan is not well-developed, but might succeed later. "Thomson died after several years of work. He had written 50 perfect chapters, but his plans for a 75-chapter novel were ultimately unrealized." "By 2010, Bob and Sally were deeply in love and about to get married. In 2006, however, they had only known each other for a month, and although their love was sincere, their relationship was still embryonic." In the quote, "embryonic" means that he took the first steps to engage with ecology. Later artists went much further, but Smithson's first steps were sincere.