Line Source - to toe in or not?

Here's one I haven't seen before. If I've missed something please re-direct me 🙂.

I have the excellent Genesis G2Jr's. The reccomendation for these, and I understand most LS speakers, is to not toe them in. Assumimg the designers know what they're talking about, why is this the case? My question is seeking a technical answer, not a 'go and try it' answer 👍.

Cheers