Yes, they can if you have the toggle enabled. As a B2B Store admin, you can enable this for your customers from your B2B settings. On your main navigation bar, click on B2B eCommerce, followed by the 'Settings' tab. Scroll down to the Pricing, Tax and Shipping section to see the toggle, 'Allow customers to request an optimal delivery date'. If this toggle is disabled, your customers will not see the optimal delivery date option during their B2B checkout process.