It may be a useful tool in some circumstances to give ideas for alternatives to search but cannot be relied on as accurate.
For example the name Guy has variations such as
G(u)y, G(u)ye(e), Guido, Guidi, Ghio, Guiu, Guitte, Guyon, Guion, Guit(t)on, Wido, Wyd, Why(e), Wye, Wyon, Wi, Why, V(u)itte, V(u)itton.
It also has diminutives such as
Guiet, Guyet, Guiot, Guyot, Guyonnet, Guyonneau, Guit(t)et, Guitel, Guitonneau, Vit(t)et, Vuittet, Guidelli, Guidetti, Guidini, Guiducci, Guiduzzi, Guidotti, Ghidelli, Ghidetti, Ghidini, Ghidoli, Ghi(d)otti, Ghiotto, Vida.
Plus augmented forms but the name thesaurus misses many of them out.
It should also be remembered, for example, that Eliza or Liza may be shortened versions of Elizabeth but they may be complete names.
As with much in family history we the researchers have to weigh the evidence before reaching any conclusion and accepting that conclusion as fact.
Cheers
Guy