During the tutorial battle, Hop has two Pokémon: A level 3 Wooloo, and his level 5 starter. This battle in Postwick is shown on the graph.
The player is not allowed to enter the grass, and thus enter a battle, on the first visit to Route 1, as they do not have any Pokémon with them.
Depending on the version, the player will either fight Bea (Sword) or Allister (Shield). This applies to both the Gym battle in Stow-on-Side, as well as the Pokémon League Semi-finals. While the two leaders have vastly different parties, the average level between them is the same in both battles.
As is tradition for the series, Hop's team changes slightly based on the starter Pokémon the player chose at the start of the game. Similarly, Leon's team also changes slightly, with Leon taking the starter that is super-effective to the players. However, the average level remains the same.
Due to the Pokémon League in Galar being a tournament as opposed to a challenge, the player is fully healed after each battle. However, the player is not able to replenish supplies after battles, and is required to immediatly proceed to the next battle in the tournament.
Due to the story, the Pokémon League is interrupted before the player is able to battle Leon, and as such the player is able to replenish supplies before battling him.
Observations
Despite being fought after Marnie, as well as the player being fully healed after the battle with Marnie, Hop in the Semi-finals has a slightly weaker team.
The level gap between the Pokémon League Finals (and the battle with Chairman Rose) and Leon is one of the largest in the series, with Leon's average level being 7.7 above that of Chairman Rose. This would suggest that the battle with Leon provides a large difficulty spike, and that holds true based on my experience playing Pokémon Sword
Boss encounters in Sword and Shield adhere very closely to the level curve, with several bosses, such as Hop on Route 7, being lower leveled than the trainers around them.
In addition, trainers tend to have levels very close to wild encounters, and in several places, such as Route 9, are actually lower levelled than the wild Pokémon the player can encounter.