Do you remember the SR strategy where a solo laner picks a support, and the carry jungler basically camps that lane in-between jungle clears? The idea was to funnel gold and xp onto that jungler (via having access to two resource streams) so that they hit their powerspikes much earlier than intended. It showed up on the Rift for a few patches before Riot nerfed it in 8.14, claiming it's a "passive and unengaging strategy" that "subverts a lot of normal laning patterns." Note that this strategy is different from duo-bot in SR, where two players share one resource stream.
The situation's more complicated in TT though. Instead of "funneling," it's referred to as "Hypercarry meta" or "Support meta," and it's been around for years. The previous designer(s) in charge of TT even went as far as to say that it's good to have a different playstyle be viable alongside the standard "Jungle meta."
Naturally, Hyper meta is a controversial topic for 3v3 players. Advocates point to the map's layout encouraging funneling and that the strategy makes for a nice change of pace. Detractors point to Riot trying to remove funneling in SR as well as Hyper's persistent dominance (for years) in 3s.
tl;dr: TT has three revenue streams: top-lane, bot-lane, and the jungle. Jungle meta distributes revenue equally so that each player has a source of income. "Funnel comp" or Hyper meta has the jungler take both jungle income and top-lane income.