How could I better convert a child object of arrays to one array of objects when flattening the parent?

I’m receiving data and scratching my head to find a cleaner way to modify the data in a singular one level array of objects:

data:

{
  dayMon: [
    {
      id: 1,
      name: 'whatever'
    }
  ],
  dayTues: [],
  dayWed: [],
  nextWeek: [
    {
      dayTues: [{
        id: 3,
        name: 'whatever'
      }],
      dayMon: [],
      dayThurs: []
    }
  ]
}

and my goal is:

[
  {
    id: 1,
    name: 'whatever'
  },
  {
    id: 3,
    name: 'whatever'
  }
]

so I created a function:

export function buildDays(data: {[s: string]: unknown} | ArrayLike<unknown>) {
  const flatDays = Object?.values(data)?.flat() || []
  if (!flatDays || flatDays?.length === 0) return null
  
  const nextWeek: unknown[][] = []
  if (data.hasOwnProperty('nextWeek')) {
    data?.nextWeek.map((day: any) => nextWeek.push(Object?.values(day)?.flat()))
  }

  const cleaned = [...flatDays, ...nextWeek?.flat()].filter(Boolean)
  return cleaned
}

but my issue falls under nextWeek an at current implementation ...reuseBlock?.flat() throws a TypeScript warning of:

Unsafe usage of optional chaining. If it short-circuits with ‘undefined’ the evaluation will throw TypeError.

Reading

• best way to convert object with arrays to array with objects and viceversa
• convert an array of objects to one object of objects
• Merge/flatten an array of arrays
• How to convert object of array of object to array of object in Javascript
• How to convert Arrays of objects of objects into one dimensional array?

In Vanilla JavaScript is there a better way to build the data into one array of objects?