Flows are tools that automate business processes by collecting data and performing actions in your org or an external system. Flows can be triggered by various events such as record creation, updates, or invocations from other processes or flows. Flows can also have decision elements that evaluate conditions and determine which path to follow in the flow. By combining the two flows into one with decision elements, the administrator can ensure that the flow runs in the correct order and updates the field on the child record after it is created by the first flow. References:
https://help.salesforce.com/s/articleView?id=sf.flow_concepts.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.flow_ref_elements_decision.htm&type=5