Gartner wisdom at its best
On one hand, "Warrilow nonetheless advocated planning for multi-cloud adoption ... so you can diversify and avoid lock-in" and on the other, "Warrilow also advocated going cloud-native".
How can you avoid lock in when you've gone native on 2 disparate platforms?
I have yet to encounter a client that has made multi-cloud work as anything other than a toilet they can flush their budget down. Every analogue between providers works somewhat differently, and tools to try and abstract away those (like Serverless) don't work in practice without significantly customising their naive default configurations or adding in numerous third party plugins that aren't portable between clouds.
You need twice the number of skills in-house, pay through the nose for cross-cloud traffic, and can't shift workloads between providers without a lot of effort and testing. Even vendor-neutral technologies like Kubernetes have significant variances in the way they work out of the box if you use the one supplied by the provider.
There will be a tiny fraction of tech businesses for whom the total failure of an entire cloud provider is an existential risk, where going multi-cloud for resilience is the necessary mitigation. There will be a slightly larger one which need certain services and facilities that are not available from a single provider that may need multiple clouds in a rational hub-and-spoke model. But for everyone else, getting it working per the board's vision is a costly pipe dream that'll never be realised.