Yes in both cases, and you'll get landscapers/gardeners who won't take the job because of it. The services around here let you pick a day, but you have no say in exactly what time or what equipment they're using. This gets you a cheaper price, and lets them work through that week's client list effectively.

The important thing is them passing on not doing your job won't affect their next one, unlike what happens if an uber driver declines too many rides.