At the end of ST:DIS 2x14, Spock recommends that

all officers remaining with knowledge of these events must be ordered never to speak of Discovery, its spore drive, or her crew again

in order to prevent the experienced series of events from unfolding again.

This left me deeply confused.

I understand that the data

gathered from the Sphere

was instrumental in

Control gaining self-awareness

Thus, the plan was to send

the ship along with the data, which is magically locked to the ship, off into the far future where it is out of reach.

So, what in the world is Spock's recommendation supposed to achieve in-universe?

Given that various methods of time travel are known in the 23rd century, it is conceivable no-one should know the data is on Discovery. But about the rest - surely, Starfleet cannot just deny the existence of the Discovery's crew. And what does the spore drive have to do with it, anyway? As far as I remember, it played a significant role during several events of the Klingon war, which are definitely noted in Starfleet's historical records, but it was completely irrelevant to Control's rise.

Major spoilers ahead (impractical to wrap this all in spoilers)

It prevents people from asking deeper questions

There's no evidence it exploded (hence the intense questioning). We're not told everything they told Starfleet, but let's assume they omitted the Sphere data debacle. Starfleet knew about Control but would be puzzled why Control was so focused on Discovery. Maybe someone would boot Control back up to ask.
If they had notified them of the Sphere data, it would have been presumed lost. By pretending that Discovery was lost, in the absence of other data, Starfleet would stop asking questions (we've seen this elsewhere when convenient lies are used to cover up things).

It stops the Section 31 time travel program

Only Ashe Tyler knows about it now (presumably, since Control purges the leadership of Section 31, the only other people to know outside of Pike's Enterprise) and he knows what's at stake if he chooses to pursue it. It's also safe to assume that this stops the Klingons from pursuing it as well, knowing that it could reawaken a monster. If they said "Oh, Burnham flew her Time Suit and Discovery to the 32nd Century", someone would say "Really? We need one of those" and then you're back in the same mess, with people trying to steal time crystals and a temporal cold war looming.