The reason you need a discrete, substantial Understand phase is not to appease designers’ need to be creative. It’s the time it will realistically take your team to express their ideas properly and get them into a form in which they can be realistically evaluated.
The understand phase is the tricky one, and it's where I find myself being challenged the most: moving pixels too soon, showing work that starts getting built too early (when it should really just be a starting point for a conversation), misinterpreting data or research, not gathering enough data or research, aligning on a framing for internal stakeholders, aligning on a framing for the people who will use the product, aligning on why this is the most important problem to be solving right now, accepting the opportunity cost of building the thing right now, aligning on how many people it will take to build the thing...
The list goes on. It's hard and messy and requires a shit-ton of meetings, one-on-ones, staring at whiteboards, and walks away from the desks. Some days I question everything and realize I know nothing.
But understanding is also the phase of the design process where I've learned the most about how to communicate and tell a story, how to match business needs with product goals, how to build relationships with cross-functional team members, and so much more. Tom Broxton's post (linked above) is a nice articulation of why it's important to know when you're in this phase, and when it's time to make the leap and build the damn thing.