YourDND is essentially a digital game engine (Janus), filled with thousands of data rows from various creators ranging from official (Wizard of the Coast or WOTC) to non-official sources (3rd party publishers, independent creators).
YourDND however, cannot replicate the Rules-as-Written (RAW) for Dungeon & Dragons (D&D) 5e. There sometimes is a lot of nuances, and complexities to what publishers and creators can come up with.
A design philosophy that YourDND belives in is: simplification and standardization. While the trade-off is you lose customization and creativity over item and layer types, but you gain more accessible streamline rules and an automated digitized gaming system which can allow DMs and players more accessibility. This can also allow easier porting of rules across different gaming systems.
Dungeon Master (DMs or GMs) are often the bottleneck for Virtual Table Top Roleplaying Games (VTTRPGs). DMs have to be storytellers, rules lawyers, actors, rules referees, and creators. These burdens can be too much, and perhaps why the ratio of players to DMs is often highly skewed, limiting access to the game to prospective players. Another design tenant at YourDND is to lessen the burden on the DM with tools to be less of a rules lawyer/referee, and allow them to be more story tellers by automating their game through Janus (the Game Engine).
Janus also allows for porting across different (TTRPG) systems, like Pathfinder 2E, allowing access to unlimited sources, while compensating publishers (big and small).
Simply put, YourDND.com is not RAW D&D, or other TTRPGs, it is a modified version of it that changes key aspects (and hopefully improves), and continues to improve as modern games do, many aspects of the VTTRPG game system.