When syncing the Estimate field from Feature in Jira ALign to Jira the tool only supports it when you use Points as estimation system for Features. Half of our customers use Member/Team Weeks on that level and therefore cannot sync the estimate to Jira. 

Syncing the estimate is important for the refinement process and as part of capacity planning and forecasting there will be increased visibility and request to see also in Jira what the work ahead will be in terms of size not just timing.

Suggestion: Enable the sync of the Estimate from Jira Align to Jira (and to ADO) regardless of the estimation system.