While Cabral's actions before reaching Brazil (i.e. swinging further west) are certainly suggestive of a deliberate exploration about Torsedillas, his actions after discovering Brazil don't require it.
My point is that it was all of Cabral's actions, both before and after discovering Brazil, which strongly suggest a deliberate attempt to look for land which is both west across the Atlantic and east of the Line of Torsedillas.
When examined individually his actions seem like happenstance. When examined collectively, however, his actions strongly indicate something else.
Cabral knew that Torsedillas had been signed. Even if his swinging west had been accidental / an individual desire for exploration / whatever, finding land which Portugal could claim on the right side of the line would be enough to justify sending a ship back to Portugal. Yes, it was expensive (any ship's cargo was worth a lot, if it survived the voyage to and from India), but having land which Portugal could claim post-Torsedillas was also very useful.
In everything I've been able to read regarding Portuguese explorations during the period, Cabral is alone in sending back a vessel with news of a discovery while the rest of the expedition pressed on. Earlier finding the Madieras, the Azores, and the Cape Verde islands didn't trigger the return of a courier with news of the discovery. Passing Cap Vert, reaching Senegal, reaching the Cape, even reaching Calicut didn't result in the dispatch of a courier back to Portugal while the rest of the expedition pressed on. The innumerable Portuguese exploration flotillas left as a unit, traveled as a unit, and, apart from losses, returned as a unit. The only time a vessel returned alone was when circumstances, almost always weather, separated that vessel from the expedition.
Despite using the same winds, same currents, and facing the same weather, Cabral "somehow" swung further west than nearly a century of previous Portuguese explorers had ever done. Despite being tasked to lead the Second Armada to India using de Gama's charts and de Gama's pilots, Cabral "somehow" swung further west than de Gama did. Despite the Sargasso being known to the Portuguese since the early 1500s, sighting seaweed led Cabral to "somehow" swing even further west. And, despite no previous Portuguese commander doing anything like it in decades of exploration, Cabral "somehow" decided to dispatch a courier back to Portugal with news of the discovery of Brazil.
If you choose to believe it was all some happy accident, so be it. I choose to believe the accumulated evidence points to something different. I choose to believe that Columbus' discoveries and resultant the Treaty of Torsedillas led the Portuguese to undertake limited exploration of the western Atlantic with an previously planned expedition which would be passing through the region in question. And I'm far from alone in believing that.
Getting back to the original scenario and as I've argued in previous threads, an absent Columbus or a Columbus who fails to gain funding delays an age of exploration by only a few years. Once Europe learns in mid-1499 that de Gama has reached India, the flood will begin. Columbus will get funding or his ideas will be dusted off, others with their own ideas will get funding, and the "discovery" of the Americas will quickly follow.
Also, as another recent thread discussed, Spain not winning the lottery in the shape of the Aztecs and Incas won't substantially effect her activities in Europe through roughly 1550.