Not necessarily. The fact that Bhaktāmara Stotra was composed by Mānatuṅga in the second half of the 6th century CE and is accepted by both Digambaras and Śvetāmbaras does not mean the sect split happened after that time. A text can be shared by both sects even if the split had already occurred earlier. Jainpedia notes both sects accept Bhaktāmara, and it also places Mānatuṅga in the 6th century. ( jainpedia.org)

In fact, standard historical summaries place the Digambara–Śvetāmbara split earlier than the 6th century: Jainpedia’s chronology marks the final split in the 2nd century CE, while other reference sources say it was probably already in place by around the 1st century CE or fully established by the 5th century CE. So the better conclusion is: Bhaktāmara became a common devotional hymn across both traditions, rather than proving a late split. ( jainpedia.org)