These building heights are a result of UDO constraints. This area is zoned to 12 stories or 150’. If I read the plans for Hillsborough II correctly the height of this 10 story building is 150’-7". I guess the extra 7" isn’t enough to quibble over.
It’s hard to know for sure but it seems the developer found it better for his case to build up to the current height maximum vs. deal with applying for a variance. Considering Glenwood One is the same situation it seems plausible building heights are being constrained by Raleigh’s UDO. Too bad … We’ve got to get more density in this town!