Washington (CNN) Robert Mueller's prosecutors dropped yet another head-scratching signal in their latest court filing Tuesday that the special counsel investigation may be wrapping up -- or maybe it's not.

Either way, they're very busy.

Senior appellate litigator Michael Dreeben told a federal judge on Tuesday that he and his co-counsel "face the press of other work" and would like a deadline extension this week in response to a request to unseal court documents in Paul Manafort's now-wrapped criminal case.

Dreeben is working with Adam Jed, a more junior appellate lawyer on Mueller's team, to respond to the request from The Washington Post. The newspaper first approached the federal court in Washington on March 7 asking for the unsealing of Manafort documents related to his breach of plea proceedings. Its request came the same day Manafort learned his first of two prison sentences, which together totaled about 7.5 years.

On Tuesday, Dreeben and Jed asked federal Judge Amy Berman Jackson, who oversaw Manafort's foreign lobbying-related case and his plea, to move the deadline for their response to the Post from this Friday to April 1.

The Post had asked the court to determine whether the prosecutors still have "compelling interest" to keep the Manafort details still under seal. The newspaper also highlighted the "quick-moving nature" of Mueller's investigation and the potential that reasons for any sealing may "dissipate." The documents the Post seeks include still-redacted portions of transcripts from two closed hearings regarding Manafort's lies during cooperation interviews and testimony, as well as evidence prosecutors presented about those lies.

Prosecutors, when they originally asked Jackson to keep the details secret, told her they related to ongoing investigations and uncharged individuals. The topics apparently related to the former Trump campaign chairman's discussions with his Russian associate Konstantin Kilimnik in 2016 and later, including about polling data Manafort shared with him intended for Ukraine.

A special counsel's office spokesman declined to comment Tuesday.

Several other recent signs have signaled that Mueller's probe may be winding down -- or at least fanning out to other prosecutors' offices. But Dreeben and Jed have stayed on.

Broadly throughout the Mueller probe, Dreeben's public court filings show he has dedicated his time to fighting defendants' attempts to dismiss indictments, media requests to unseal documents and appeals including a mystery grand jury matter involving a foreign-owned company that's awaiting Supreme Court action. In his time working for Mueller, Dreeben has also argued a few unrelated Supreme Court cases. (He is one of the high court's most frequent and accomplished litigators, having argued there more than 100 times.)

The special counsel's office has previously said Dreeben and Jed work full time for Mueller, and their court filing Tuesday indicated they still work for the special counsel.

Dreeben, by all appearances, works long hours still. He regularly arrives to the office minutes after the notoriously early Mueller.

Others on the special counsel team have peeled off to work for other parts of the Justice Department, while the senior prosecutor over the Manafort cases, Andrew Weissmann, prepares to leave government-side work for a law school position.

FBI agents and prosecutors continue to swarm in and out of Mueller's office daily -- and even have visited the courthouse for non-public matters at least twice since Manafort's cases neared their end, according to CNN's reporting.