One of my favourite Alliums is Allium schubertii, and this image has all the hallmarks of the schubertii variety. I grew it for many years in Riverview, and loved its starburst structure, of which, this photo is an excellent example.
From the Database, here are some of the photos to compare it with:
Here one can see the 'Starburst' effect.
The thickness of the partial stem that is shown, would also be more typical of the shorter plant of Allium schubertii. Whereas Allium giganteum is on a very tall but slender stem, and seems a giant, one of the tallest of the Alliums.

Just some random observations and conjectures.

@HemNorth here is a picture of the whole plant in bloom.


Here is the pic of the bloom. Doesn't look like a schubertii



This year my alliums were shorter than normal. I only have the one type of alliums.

@Frenchy21 - You are absolutely right - that blossom is not Allium schubertii. Thanks for showing the bloom!
Could you submit the second blossom into the Allium giganteum Database section, please? It is a lovely example. Thanks for responding and correcting my impression!

@HemNorth - Thank you for the thumbs-up I checked the pics in the Allium database pics and realized that I already posted them in the Giant Onion (Allium giganteum 'Globemaster') category. Mine looks very much like those pics. I will post the pic of the allium seedhead there too