I've complained and made suggestions to both Adobe and Corel about this particular subject since the 1990's.
Honestly, I see no legitimate reason why Adobe and Corel can't include an
option for sizing type objects according to cap height.
Sign making applications like Flexi aren't doing anything special to make something like 1" tall letters actually 1" tall. The software examines a given typeface's data -particularly its baseline and cap line settings. It uses that distance between the base line and cap line as a reference to not only make a 1" tall letter 1" tall, but also making line spacing adjustments, like if you want 3 lines of 1" characters with 1/2" of space between each line.
Selecting a capital letter and numerically sizing it is a kludge. The work-around only works accurately with sans-serif letters featuring at least some capital letters bottom and top parts that run truly parallel to the baseline. There are many typefaces that don't do that. Serif typefaces have parts the dip below the baseline and rise above the cap line. Script typefaces are all over the map in that regard.
If Adobe and Corel would at least offer the option to do with sign making apps have done for decades it would offer a greater level of consistency, especially when sign companies are receiving customer generated artwork.
If Adobe and Corel refuse to offer this kind of type function perhaps some third party might be able to do it. If I knew enough about computer programming and creating plug-ins I would certainly make such a plug-in.
First go to "Edit > Preferences > General and tick "Use Preview Bounds". You'll only need to do this once.
Edit: At first I thought this wasn't showing up in Illustrator CC. I had the Photoshop CC window open instead.