High tone

My son will turn 3 in January. His teacher said they’ve noticed he has “high tone” Like when they hold his hand to go up the steps he’s very stiff was her example. She said he’s fine now but when he’s older he likely won’t be athletic (kinda shocking to hear) He was a later walker (closer to 15 months) walked on tippy toes a bit (no longer). In general he doesn’t seem as strong or coordinated as his older brother (who was always ahead of the game physically compared to his peers) but otherwise no glaring red flags to me. He just started a few months ago and only goes 2 mornings a week for 2.5 hours a day. Im confused as to her quick assessment and expressing such a limiting concern. I asked his aunt or is in OT who stated she’s never seen any obvious signs. I will ask his pediatrician at his well check. Is this appropriate for a teacher to conclude?