The Vanguard rep gave you bad information regarding a need to wait. Rollovers from a 401(k) are not subject to any limitations on the timing of rollovers. The 1-year rule does not apply. If fact, under self-certification the rollover is required to be completed as soon as is practicable, so you can complete the rollover of exactly $515 even before you receive the distribution of the $515 (adjusted for investment gain or loss) from the traditional IRA.
From IRS Rev. Proc. 2020-46:
The contribution must be made to the plan or IRA as soon as practicable after the reason or reasons listed in the preceding paragraph no longer prevent the taxpayer from rolling over the amount distributed (which includes any amount withheld for income tax) or a lesser amount if the taxpayer wants to roll over less than the total amount distributed or if part of the amount distributed is ineligible for rollover. This requirement is deemed to be satisfied if the contribution is made within 30 days after the reason or reasons no longer prevent the taxpayer from making the contribution.
