Servo - first positioning too fast after reboot

Hello,
I am currently trying my hand at esphome and a servo motor.
So far so good. Everything is actually working. But I have the problem that the first positioning after a restart is done too fast.
The parameter “transition_length” doesn’t seem to work for the first positioning. However, the parameter has an effect on the next positionings.
How can I ensure that the first positioning run is also slow?

My source code is certainly not perfect. I’m just getting started with it …
I hope I have posted the source code here correctly.

esphome:
  name: wandthermostat-wohnzim
  friendly_name: wandthermostat-wohnzim
  platform: ESP8266
  board: d1_mini

# Enable logging
logger:

# Enable Home Assistant API
api:
  encryption:
    key: "xxxxxxx"

ota:
  password: "xxxxxxx"

wifi:
  ssid: xxxxxxx
  password: xxxxxxx

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "Wandthermostat-Wohnzim"
    password: "xxxxxxx"

captive_portal:

output:
  - platform: esp8266_pwm
    id: pwm_output
    pin: D1
    frequency: 50 Hz
servo:
  - id: thermostat_servo
    output: pwm_output
    restore: False
    transition_length: 1.0s
    auto_detach_time: 2s


number:
  - platform: template
    name: Wandthermostat Servo Control
    id: wandthermostat_servo_control
    icon: mdi:thermometer-auto
    device_class: TEMPERATURE
    min_value: -100
    max_value: +100
    step: 1
    set_action:
      then:
        - servo.write:
            id: thermostat_servo
            level: !lambda 'return x / 100.0;'