Стало любопытно, погуглил. В двух тредах на СО пишут:
The size of the buttons automatically gets adapted to the content of the buttons. You can't change the size of the buttons yourself.
On certain devices there are problems when the content is not completely trimmed. So:
Make sure you are setting a Button text
Make sure all leading and trailing blanks, new lines are removed.
Да можно прям документацию telebot зайти,там все прям збс с примерами, одна из лучших документаций