I was not aware of this limit at all!
However do we really need that many cosigners for a multi-sig wallet. Possibly few will mess the whole then and ruin the original goal of creating that multi-sig wallet.
There are many things like that which you can do on electrum wallet on computer than phone, 6 of 6 multisig and more keys and signers is not on phone electrum.
There are some few reasons you may want to use more than 5 keys, like a family of 6 or more, it may also be required in business. If a single person wants to use multisig, 2 of 3 is enough.