The inclusion of Gen 8 movesets in BDSP (Brilliant Diamond and Shining Pearl) can be seen as a deliberate design choice rather than an oversight. While there may be instances where certain Pokemon have moves missing from their usual movesets due to changes introduced in Gen 8, the availability of these moves in TMs can be seen as an attempt to provide players with a way to access these moves.
It’s important to note that the main purpose of BDSP is to faithfully recreate the original Diamond and Pearl games, which were released in Gen 4. As such, the developers may have wanted to maintain the integrity and nostalgia of the original games by sticking to the movesets available in Gen 4.
However, the addition of Gen 8 moves through TMs can be seen as a way to provide players with some of the new move options introduced in later generations. This allows for more diverse and strategic gameplay, as players can choose to teach their Pokemon these new moves if they so desire.
That being said, it is understandable that some players may feel that certain Pokemon are missing out on moves that they would usually have in more recent generations. This can be frustrating, especially if a Pokemon’s movepool has been significantly altered in Gen 8.
In terms of the availability of these moves in TM form, it is worth noting that the Gen 4 TMs do not include all the moves introduced in Gen 8. This could be seen as a limitation imposed by the developers, perhaps to maintain balance or to ensure that the game stays true to its Gen 4 roots.
The inclusion of Gen 8 moves in BDSP can be seen as a deliberate design choice to provide players with additional move options while staying true to the original Gen 4 games. The availability of these moves through TMs may be limited, but it still allows for some degree of customization and strategic gameplay. While it may be disappointing for some players to see certain Pokemon missing out on moves they would usually have, it is ultimately a decision made by the developers to maintain the authenticity and nostalgia of the original games.