When I build my pond I just dropped the plants in and the prosperedd. I had to clear the pond and when I got the following plants the planting advice was rather precise. Does it really matter?

Hippuris Vulgaris planting Mares Tail (Hippuris Vulgaris), shallow water plant, is a native plant useful as a marginal and an oxygenating aquatic plant. Planting depth 3” to 8” inches of water above soil level.

Hydrocotyle sibthorpioides 'Variegata' will spread to form a dense mat of foliage that offers excellent cover for wildlife. Height: 6" inches Spread: 100cm 39" inches Planting depth 10” inches.

Mimulus Ringens Grow submerged in the shallow margins of ponds with the crown to a maximum depth of up 6" inches below water level. Choose a position in sun or dappled shade.

Iris Versicolour grow submerged in the shallow margins of ponds with the crown to a maximum depth of up 6" inches below water level.

I would go with the advice provided as you're more likely to have success.