Black Mesa also:
-referenced Gordon's ponytail which was just a small development tidbit and presented it as part of the lore
-injected Kleiner, Eli and Barney based on what was implied in HL2 and Blue Shift even though they didn't exist when HL1 came out
-injected the whole Freeman prophecy bullshit with the Vortigaunts which were nothing but generic enemies when HL1 came out
-completely redesigned Xen to the point where it holds zero resemblance to what it was in HL1
And before you pull any excuses, stop. Recommending mods like this as someone's first experience with a series is what led to the demise of the DOOM community (before DOOM 2016) and the STALKER community (before the war/STALKER 2). Brutal Doom caused an infestation of COD idiots that didn't understand DOOM and Anomaly/GAMMA caused an infestation of milsim idiots that didn't understand STALKER, and both started judging DOOM/STALKER as if they were long time fans and understood what the series was about.
By promoting fan mods as the first experience with a series because "they're totes like the OG's and like better in every way dude", and excusing this behavior, you are the very cancer that destroys this hobby, and I can only wish for the same destruction to happen to your beloved series.