Are Pro versions of perks automatically applied when unlocked in the middle of a match?

During a match, I saw the message "Assist Counts As Kill". I was using the standard Hardline perk which provides access to killstreaks one kill earlier. At the end of the match, the game informed me that I had unlocked the Hardline Pro perk which adds the bonus "every two assists count as one kill towards your killstreak." Is this what I saw earlier in the match or are there situations (i.e. you do 95% of the damage) where assists always count as kills?

Yes they are applied in mid match.

There is no situation where an assist will ever equal a kill unless you have Hardline Pro

Actually, they are only applied after you spawn, because the game still recognizes that you have Hardline when you spawn until you die, so if you unlock Hardline Pro, and Assist will not count as a kill until after your next spawn.