There is a great deal to know about the details of the time as well. What was the surface. Indoor or outdoor. Straight or on a curve (really only applies if indoor). Hand-held times can certainly vary by as much as a second for something like 100m. Official timing is based on equipment that is synched up with the starter’s pistol and on the finish line. Typically, when someone does a handheld time and does ‘on your marks, get set, go’ there is a lag before the clock is started. 1 second is huge in the 100m.
That being said…I would get some confirmation times. Run a race if you can and see if this was a valid time or just a poorly clocked one. If it is valid, send validation to the coaching staff with a letter. Explain your situation. They may want to see you run themselves.
I agree that if those times are indicative of your current ability, coaches will be all over you. Yes, they prefer someone with multi-event talent. The 100m also translates well to the 200m, 4x100m relay, Sprint Medley and possibly even jumping (long and triple jumps primarily). If you are that good untrained, they may be willing to take the chance to teach you another event or two.