Have you checked the ACS website for info and photos? Apparently maintains a very narrow profile. https://conifersociety.org/conifers/picea-mariana-wellspire/

this is the proper name: Picea mariana 'Wellspire' .. often you get better research results when using such..

look at the second pic here... does it look like 8 feet is enough to you?

https://duckduckgo.com/?t=ffcm&q=Picea+mariana+%27Wellspire%27&iax=images&ia=images&iai=https%3A%2F%2Fpics.davesgarden.com%2Fpics%2F2006%2F03%2F07%2Fconifers%2F404bcd.jpg&pn=1

as trees.. conifers never really stop growing.. how long will it take to look like the one above.. 10.. 15.. 20 years .. will you care in 20 years???

10 feet would be better.. and 12 even more so ...

and your landscaper should know all this ... hmmmmph ... maybe his brother has a bunch for sale ...

ken

btw:.. this pencil thin tree on the corner of the house is going to look very weird in 10 or 5 years ... if it is 1o feet taller than the house... so it might matter what your house looks like.. whether a thin tree at the edge would look good .... care to post a pic of your house?