By a quick glance over this thread, no one mentioned one rather important property of Shamir Secret shards: a single shard doesn't reveal anything about what it encodes. More specifically, if you have less shards than the minimum required, none of those shards reveal any information about what they encode.

This is different if you simply split mnemonic recovery words into parts, where each part reveals a subset of the mnemonic recovery words.

There are reasons to evolve BIP39 recovery words and somebody has to make the first steps. My only problem with Trezor's new approach is that they are at present likely the only ones who support it. I don't know if other wallets will follow up and thus interoperability is hampered or rather cut off.