No. Descriptions measured in weeks are official language, not a commitment, and your case still depends on vetting, the EB-1 or EB-2 determination, visa availability and an interview. Give your employer a range with conditions attached, and make clear that a paid fee does not authorize work. The promise that breaks is the one made from a published description rather than from a granted document. A description tells you how a process is meant to run; only the grant tells you when your own case actually finished.
How to phrase a start date you can stand behind
Review your category and chargeability early, because they shape when a visa can be available and when an interview can happen. Then tell your employer what is fixed, your application date and your document readiness, and what is not. Lawful permanent residence generally permits work.
Before it is granted, any independent work authorization must be assessed separately; the Gold Card application alone does not provide it. A qualified estimate holds up; a confident date invites a broken promise. Give the employer a conditional sequence instead of a date: application filed, vetting completed, determination made, visa available, interview attended, admission granted, work begins.
Naming the steps turns a broken promise into an expected delay, and it lets an employer arrange cover rather than discover a gap. Where a start date is contractual, ask for it to be defined by reference to admission rather than to a calendar day that nobody involved controls.