Looking back at this, it's possible he's saying that this is the only "direct" sequel. Dracula's Daughter doesn't feature Dracula. Son of Dracula doesn't feature Dracula. The only films that feature Dracula after the 1931 film are crossovers like House of Frankenstein.
Now, Renfield isn't present in those films since he was supposed to be dead in the 1931 film, so that would be an issue. Renfield appears to retcon it so that Dracula let him live to serve.
Other than that, there's a possibility all these films are the same universe.
1899 - Frankenstein
1899 - The Bride of Frankenstein
1931 - Dracula
1931 - Dracula's Daughter
1931 - The Invisible Man
1935 - Werewolf of London
1939 - Son of Frankenstein
1939 - The Wolf Man
1940 - The Invisible Man Returns
1940 - The Invisible Woman
1941 - Invisible Agent
1942 - The Ghost of Frankenstein
1943 - Frankenstein Meets the Wolf Man
1943 - Son of Dracula
1944 - House of Frankenstein
1944 - The Invisible Man's Revenge
1946 - House of Dracula
1948 - Meet Frankenstein
1951 - Meet the Invisible Man
2023 - Renfield
Technically speaking, if we include novel crossovers as canon then The Mummy's Hand series is canon. Then, if we include the sequel mobile game that you can't even find anymore of The Mummy (2017), then The Mummy/Scorpion King films are canon because that game crosses over with The Mummy's Hand. The Mummy (2017) had references to the Creature from the Black Lagoon so that would be canon too. The longest running shared universe, lol.