I've tried explaining this many times, but round 438.
People misinterpret the professional seasons thing with regards to the expansion draft way too much... They point to a part of the CBA that doesn't apply here. Starting at age 20, 10 games are needed in any league to count as a professional season, which is true for free agency, but not true for waivers or other professional season definitions. The CBA is confusing and difficult for anybody well versed in it, let alone fans. The simplest explanation I've been told, by an NHL organization's CBA expert, look at the waivers clock and the starting year. Professional seasons start there regardless of games played, exceptions to that require approval by NHLPA and NHL. Which depending on who you ask, you'll get a different answer on Timmins.
If you want a name to look at... Gustav Olofsson:
-Signed in 2014 to a contract starting in 14-15 (waivers age set at 20)
-Played 8 games in the 13-14 season for Iowa Wild on ATO (not on SPC so this season doesn't count)
-Played 1 game in 14-15 before being injured for the season (read below threshold people frequently state for professional season, and one was not accrued for free agency)
-Played 2 full seasons in 15-16 and 16-17 accruing 2 professional seasons for free agency
-2017 Eligible for Vegas to draft and was left unprotected
NHL Expansion Draft protected list revealed
2 professional seasons accrued for free agency, 3 for waivers (meaning would have to be sent through in 17-18), had to be exposed in Expansion Draft.
What the Avs will argue in their waiver is the Timmins had a full season wiped out and only had 2 development years and thus should be exempt. It is a good case, but other teams and NHLPA will point right to Olofsson.