How can one reconcile the statement that the open call to Islam began at the end of the third year of the Prophetic Mission with its connection to 'Umar ibn al-Khattab's conversion, which occurred in the fifth or sixth year?

Public preaching began at the end of the third year of the Prophet's prophethood, as mentioned by Ibn Ishaq, when Allah commanded him to proclaim His message after three years of prophethood. It is incorrect to say that it began with the conversion of 'Umar ibn al-Khattab, may Allah be pleased with him, as 'Umar embraced Islam in Dhul-Hijjah of the sixth year of prophethood, after some Companions had migrated to Abyssinia. His conversion had a significant impact on strengthening the Muslims and enabling them to pray at the Kaaba. The Prophet, may Allah's peace and blessings be upon him, had prayed to Allah to strengthen Islam through him or through Abu Jahl.