'it's possible to compare means of two independent groups without considering standard deviations" ?

For example:

Control Group: mean +- standard deviation 50 +- 10 mm

Experimental Group: mean +- standard deviation 100 +- 30 mm

I am very surprised with the following conclusion made by a dentist friend mine

"Then we say there was an increase of mean 100% between groups !!"

(100 - 50) / 50 = 1 = 100%

However this conclusion seems odd to me, as it disregardes the variability of the data.

TIA

Ivan