No. The two are not the same product and should not be confused.
A Structured Installment Sale (SIS) is a sale under IRC §453, the installment-sale method, with the resulting payment obligation assigned to an assignment company via a non-qualified assignment (sometimes called a "structured sale" or "non-qualified structured settlement"); the assignment company funds it with a fixed annuity it owns. It borrows the assignment mechanics personal-injury structured settlements have used since the 1980s, but those rely on IRC §130, which does not apply to a sale. Periodic payments are owed by an assignment company, usually affiliated with the life insurer, which funds them at closing with a fixed annuity it owns from a highly rated U.S. life insurer.
The "Deferred Sales Trust" is a marketed product with no specific IRC code section, typically structured around an unrelated third-party trust acquiring the property in exchange for an installment note. The IRS has issued no published guidance approving it, multiple promoters operate under it, and the related "monetized installment sale" structure drew a negative Chief Counsel analysis (CCA 202118016) and 2023 proposed regulations to make it a listed transaction (REG-109348-22).
If a client comes to you with a "deferred sales trust" proposal, we recommend they ask for the specific IRC section that authorizes the deferral. There isn't one. For the installment method itself the answer is IRC §453(a) through (j), §453A, and §483 on imputed interest. The assignment structure layered on top has no IRS ruling specifically approving it, so the client's own CPA or tax attorney should review the documents.