No, 'wachten iemand' is not an older or dialect form of 'wachten'. It is simply incorrect in standard modern Dutch. The correct phrasing requires the preposition 'op', so you must say 'wachten op iemand' (to wait for someone). If you saw 'wachten iemand' in a sentence, you may have misread the word order or encountered a typo.
In Dutch, the verb 'wachten' always needs 'op' when you specify who or what you are waiting for. For example: 'Ik wacht op de bus' (I wait for the bus) or 'Wij wachten op jou' (We wait for you). Without 'op', the sentence becomes ungrammatical and confusing. The only exception is when 'wachten' is used absolutely, meaning without an object, like 'Ik wacht' (I am waiting). But as soon as you mention a person or thing, 'op' is mandatory.
You might be confused by word order in a sentence like 'Ik wacht, Jan komt eraan' (I wait, Jan is coming). Here 'wacht' stands alone, and 'Jan' is part of a separate clause. Another possibility is a typo where 'op' was accidentally omitted. In older Dutch texts, you sometimes see 'wachten' with the genitive case (e.g., 'wachten des heils' meaning 'waiting for salvation'), but that is archaic and never used with a person. In modern Dutch, 'wachten iemand' is simply a mistake.
To avoid this error, always remember the pattern: wachten + op + someone/something. Practice by writing sentences like 'Ik wacht op mijn vriend' or 'Hij wacht op het nieuws'. If you are reading a text and see 'wachten iemand', check if 'op' might have been left out due to a typo or if 'iemand' is actually part of a different phrase. For example, 'Ik wacht, iemand komt' (I wait, someone comes) is correct because 'iemand' starts a new clause.
Your best next step is to drill this preposition with online exercises or flashcards. Many free resources like Dutch grammar websites or apps offer practice with verbs and prepositions. Focus on 'wachten op' until it feels automatic. If you encounter unusual forms in historical texts, note that they are not used in everyday conversation. Stick to the standard structure, and you will sound natural and correct.