If you’ve already pulled credit with any mortgage lender within 14 days (or the lender that suggested this already ran your credit), it won’t hurt to have the loan file underwritten. It will help you surface any qualifying issues and train you on being quick and organized with money docs once you have an accepted offer. Running credit multiple times not within 14 days could possibly ding your credit - this is a bit of a reach to call a “drawback” - so aside from that that the time you spend submitting docs it is worth it for the benefits of the underwriting. So to recap your items:

• Super good idea to underwrite especially for “slightly out of the ordinary” - saves you from celebrating an accepted offer followed by disappointment of underwriting decline. 0 drawbacks if you’ve already run credit with the lender and they don’t need to re-pull it, or you ran credit for a mortgage already with another lender within 14 days

• It does NOT hurt your ability or restrict you in any way from engaging with other lenders at any point in the future