The mentioned alternative from Würth would be ok from the point of view of the core geometry, while the initial permeability is probably a bit too low for best values.
But, as is well known, the properties of the ferrite material are subject to a tolerance of up to +/- 20 % … so one would have to make a comparative measurement, or just be on the safe side and choose the known.
The initial permeability of ferrite materials is
- 620 for ferrite material 4W620
- 800 for #43 ferrite material
No information can be found quickly about the complex permeability (u vs frequency) of the material 4W620.